How to Sew Clamshells Using the EPP (English Paper Piecing) Method – A Beginner Friendly Tutorial

Clamshell EPP – A Tutorial

Love the look of EPP clamshells but not sure where to start?

You’re not alone! Clamshells are one of those patchwork designs that look incredibly intricate, so it’s easy to assume they’re difficult to sew. The good news is they’re much easier than they look – promise.

In this tutorial, I’ll show you the exact method I use to create smooth, beautifully aligned EPP clamshells using English Paper Piecing (EPP) and a simple appliqué technique. It’s my go to method for clamshells. I use it in my own patchwork bags and pouches and I prefer it for its neatness and accuracy over needle turn clamshells.

Whether you’re making a quilt, a pouch, or another patchwork project, this beginner-friendly tutorial will walk you through every step – from glue basting your first clamshell to creating a finished patchwork panel.

So grab a cup of tea, your favourite fabrics, and let’s get started!

What You’ll Learn

In this tutorial, I’ll show you how to:

Cut and glue baste your EPP clamshells.
Prepare your foundation fabric.
Join clamshells into perfectly aligned rows.
Appliqué the rows using a blind hem (slip) stitch.
Build a beautiful clamshell patchwork panel.
Finish the panel ready for quilting or turning it into a bag or pouch.

What Makes Clamshells Different?

If you’ve sewn traditional English Paper Piecing before, clamshells work a little differently.

With shapes like hexagons or diamonds, each paper shape is sewn directly to the next along the edges.

Clamshells, however, are not joined edge-to-edge. Instead, each row of clamshells is lightly stitched together at the points to form a chain, then appliquéd onto a foundation fabric using a blind hem (slip) stitch. Each new row overlaps the previous one, gradually building your patchwork panel.

It might sound a little unusual at first, but once you’ve sewn your first row, the process quickly starts to make sense. It’s also one of my favourite ways to sew them because you get all the accuracy of English Paper Piecing, while creating those beautiful flowing curves that clamshells are known for.

What You’ll Need

Before we begin, gather the following supplies.

Essentials

Fabric scraps for your clamshells – at least 1/2″ bigger than your paper templates
Clamshell EPP paper templates
Foundation fabric
Fabric glue pen
Appliqué glue
Needle and thread
Small, sharp scissors
Erasable fabric marker or pencil
Iron and ironing board/pressing mat

My Favourite Tools

These are the products I personally use whenever I’m sewing EPP clamshells.

Sue Daley Milliners Needles (Size 11) – They’re beautifully fine and glide through multiple fabric layers with ease. And the best part – they are easy to thread. Bohin also do a nice size 10 Milliners needle, but I still prefer Sue Daley’s.
Bottom Line Thread – Thin, strong, and almost invisible once stitched.
Sewline Fabric Glue Pen – My favourite for glue basting and can be used for positioning clamshells before stitching if you’re on the go.
Appliqué glue – perfect for holding your clamshells down before stitching in place. I use Sue Daley appliqué glue or Roxanne Glue Baste It.
Clover Wonder Clips or Alphabitties – Perfect for keeping rows organised while you sew.
Frixion Pen – Great for tracing around templates, as the marks disappear with heat, I also use a chalk marker or fabric pencil .

Before We Begin…

The method in this tutorial can be used with any size clamshell template and for almost any project.

For this tutorial, I’ll be demonstrating the process using 3″ clamshells from my Patchwork Clamshell Zipper Pouch pattern. However, the same techniques can be used to create quilts, cushions, bags, pouches, and other patchwork projects.

One thing to keep in mind is that although you’re using English Paper Piecing to create the clamshell shapes, they aren’t sewn together in the same way as traditional EPP.

Instead of joining each shape edge-to-edge, the clamshells are first joined into rows with a few small stay stitches at the points. Each row is then appliquéd to a foundation fabric using a blind hem (slip) stitch, with each new row overlapping the one before it.

It sounds a little different at first, but don’t worry—I’ll guide you through every step.

Let’s get started!

Step 1: Cut Out and Glue Baste Your Clamshells

The first step is to cut out and glue baste all of the clamshells you’ll need for your project.

The number of clamshells and the layout will depend on what you’re making. I find it helpful to arrange my paper templates into the finished layout first, then use this as a guide so I know how many I need to make. As a general rule you want to make your patchwork panel ½” bigger then the finished size you’ll need for whatever you choose to make.

For this tutorial, I’ll be using 3″ clamshells for the large size pouch in my Patchwork Clamshell Zipper Pouch pattern.

Trace and Cut the Fabric

Place a clamshell paper template onto the wrong side of your fabric and trace around it using an erasable fabric marker or pencil. Then, using a small pair of sharp scissors, carefully cut around the traced line, leaving a ¼” seam allowance.

If you’re using an acrylic template, simply trace around the outside edge. Most acrylic templates already include the ¼” seam allowance, so you can cut directly on the traced line.

Because of the tight curves, scissors will give you a much cleaner result than a rotary cutter.

Tip: I like using a Frixion pen to trace my clamshells because the markings disappear with the heat of the iron.

Glue Baste the Top Curve

Place the fabric right side down and centre the paper template on top.

Run a thin line of fabric glue along the top convex curve, from one point to the other.

Fold the fabric over the paper and press it firmly into place. I like to start about one-third of the way around the curve, then work from the opposite side back towards the middle.

As you fold the fabric over the paper, firmly smooth it around the curve with your finger. This helps create a smooth, rounded edge without puckers or folds.

Take your time with this step. Good preparation here makes the rest of the process much easier and results in beautifully smooth clamshells.

Tip: Pay particular attention to the points where the curve begins and ends. Keeping these nice and crisp will help your rows line up accurately later.

Note: Only the top convex curve is basted. Leave the two lower concave curves unturned, as this seam allowance is needed to joint the next row of clamshells.

and that’s it! You’ve officially basted your first clamshell. Once you have a whole pile like the following, you’re ready for the next step.

Step 2: Arrange the Clamshells into Rows

Once all of your clamshells are basted, arrange them into the layout for your project.

I like to keep each row together using Clover Wonder Clips or Alphabitties. It keeps everything organised and makes the sewing process much easier.

Step 3: Join the First Row

Take the first two clamshells from your first row and place them right sides together, aligning the points where the top curve begins.

It helps to gently fold the fabric back at the points so they’re easier to see.

Using a needle and thread, sew the two clamshells together with three small stay stitches, stitching directly through the fabric at the points.

There’s no need to knot your thread, as these stitches simply hold the row together while you appliqué it to the foundation fabric.

Continue joining the remaining clamshells in the row the same way until you’ve created a chain.

Tip: Keep your stitches as close to the points as possible. This helps the clamshells stay straight and evenly spaced when they’re appliquéd to the foundation fabric. They also act as a guide for lining up your next row of clamshells.

Step 4: Prepare the Foundation Fabric

The first row of clamshells is appliquéd onto a piece of foundation fabric. This is something for your clamshells to attach to so the top curves of the first row don’t get cut off.

As a general rule, I like my foundation fabric to be 1″ longer than the first row of clamshells, leaving approximately ½” of overhang on each side.

For the height, simply cut your foundation fabric ½” taller than the finished height of your clamshells.

For example:

2″ clamshells: Cut the foundation fabric approximately 2½” high.
3″ clamshells: Cut the foundation fabric approximately 3½” high.

This gives you a little extra fabric to work with and plenty of room for trimming later if needed.

Mark the Centre Line

Fold the foundation fabric in half lengthwise and press it with a hot iron to create a crease.

Open the fabric back up again. This crease marks the centre of your foundation fabric and will be used as a guide when positioning your first row of clamshells.

Tip: I prefer using a pressed centre crease rather than measuring and drawing a line. It’s quicker, more accurate, and disappears once the panel is complete.

Step 5: Position the First Row

Place the first row of clamshells onto the foundation fabric, aligning the top edge of the clamshells with the centre crease.

Centre the row across the width of the foundation fabric.

Apply a small amount of applique glue to the back of each clamshell to hold the row in place, then press with a hot iron to set the glue.

Tip: To avoid a sticky mess of applique glue it helps to apply glue to only a couple of clamshells at a time and only tiny dots away from the edge of the clamshell.

Step 6: Appliqué the First Row

Using a blind hem stitch (slip stitch), appliqué the first row of clamshells to the foundation fabric. This is the same stitch commonly used for needle-turn appliqué.

I find it easiest to work in the direction of my sewing hand. If you’re right-handed, work across the row from right to left. If you’re left-handed, work from left to right.

Take a tiny stitch in the foundation fabric, then pass your needle under the folded edge of the clamshell. Continue working your way along the top curve, taking small, even stitches.

If you’re new to this stitch, watch the short video below to see exactly how I sew it.

Continue across the row until all of the clamshells have been stitched in place.

Tip: Your needle should always enter the foundation fabric just beneath the folded edge of the clamshell. This helps keep your stitches almost invisible from the front and gives your clamshells a beautiful hand-finished look.

Step 7: Remove the Papers

Once the first row has been appliquéd, gently remove the paper templates from the back of each clamshell.

Gently ease the paper template out by sliding it sideways towards one of the open curves at the side of the clamshell. Trying to pull it straight out through the bottom of the clamshell is much more difficult and can distort the fabric.

Once the papers have been removed, give the row another gentle press with a hot iron.

Step 8: Add the Remaining Rows

Join the next row of clamshells together using the same stay stitch method as before.

Position the row so the top centre of each clamshell lines up with the stay stitches joining the row above. Once you’re happy with the placement, apply a small amount of fabric glue to the back of each clamshell and press with a hot iron to set the glue.

Using the same blind hem stitch, appliqué the row to the previous row of clamshells. Once complete, remove the paper templates and press the row flat.

Continue adding rows in the same way until your patchwork panel is complete.

See! Not so bad after all right!?

You can now sew perfect little clamshells too.

Whether you turn it into a pouch, a bag, a quilt, or another patchwork project, you’ve learnt a beautiful EPP technique that you’ll be able to use again and again.

Don’t be surprised if making clamshells becomes a little addictive!

Tips for Success

Keep your rows organised as you sew.
Press after each row to keep your panel nice and flat.
Remove the papers after each row has been stitched. This makes positioning the next row much easier.
Take your time with the glue basting and appliqué. A little extra care at each step will reward you with beautifully smooth, accurate clamshells.

Common Clamshell Mistakes (and How to Avoid Them)

If your first few clamshells aren’t perfect, don’t worry! Like any new sewing technique, they become much easier with a little practice.

Here are a few common issues and how to fix them.

My clamshells don’t line up.

This usually happens if the stay stitches weren’t sewn exactly at the points of the clamshells. Taking a little extra care when joining the rows will help keep everything straight and evenly spaced.

My curves look puckered.

When glue basting, make sure you firmly smooth the fabric around the top curve as you fold it over the paper template. Taking your time during preparation makes a huge difference to the finished result.

My appliqué stitches are showing.

Try taking smaller stitches and catch only a few threads on the very edge of the clamshell with each stitch. Using a fine needle and thread also helps your stitches blend into the fabric.

My rows aren’t straight.

Use the pressed centre crease in your foundation fabric as a guide when positioning the first row. From there, each additional row naturally follows the one before it.

Clamshells On the Go

One of the best things about English Paper Piecing is that you can take it almost anywhere. Whether you’re waiting for the kids, travelling, or simply relaxing on the couch, it’s the perfect project to pick up whenever you have a few spare minutes.

So how does that work with clamshells?

The trick is to do a little preparation before you leave home.

Cut your foundation fabric ahead of time, as this is much easier to do with a rotary cutter, ruler and cutting mat.

If you’re working from fabric scraps, clamshells are easy to trace, cut and glue baste while you’re out and about. I like to keep a small project pouch stocked with my fabric, paper templates, scissors, glue pen, needle and thread so everything is ready to go.

Don’t have an iron handy? No problem! If you don’t like waiting for liquid appliqué glue to dry, a Sewline Glue Pen works brilliantly for basting clamshells on the go. It holds the fabric in place well enough to keep you stitching until you get home.

When it’s time to remove the papers and add the next row, simply remove the papers and use a seam roller to firmly roll along the top curved edge of the clamshells. It isn’t quite the same as using a hot iron, but it works surprisingly well when you’re away from your sewing room.

With a little planning, clamshells become the perfect portable sewing project—ready whenever you have a few quiet moments to stitch.

Try This!

You don’t always have to sew your clamshells the same way.

Try turning them upside down so the rounded curve faces down instead of up. The overlapping rows create a gorgeous scalloped design that looks completely different, even though you’re using the exact same templates.

Just remember: if you’re using directional fabrics, make sure your prints are facing the right way before you start cutting. Flipping the clamshells changes the orientation of the fabric, so it’s worth checking before you begin.

It’s such a simple change, but it opens up a whole new world of design possibilities!

Now That You’ve Got the Process Down Pat… Here Comes the Fun Part!

You’ve learnt how to cut, baste, join and appliqué your clamshells, so you’ve got the process down pat… now comes the fun part!

It’s time to turn all those pretty little clamshells into something you can actually use.

My Patchwork Clamshell Zipper Pouch pattern takes your patchwork panel and turns it into a practical, fully lined zipper pouch, complete with a contrasting base and beautifully boxed corners.

And now there are two sizes to choose from, including the brand new Small size. Because let’s be honest, those little 2″ clamshells are just too cute.