Sew curved shapes together into stylish scalloped patchwork with our clamshell quilt template and how to guide. This soothing project to make is the perfect scrap-buster so reach for your fabric off cuts and give them a new lease of life. We’ll show you step by step how to sew practise your clamshell skills with a beginner cushion project, then once you’ve mastered the art of the main technique, it’s easy to adapt this project into a full scale clamshell quilt pattern. This project was designed by Jo Avery for Love Patchwork & Quilting magazine.
Free clamshell template
Before you begin, you’ll need to download our Clamshell quilt template (PDF)
How to make a clamshell cushion
- Neutral coloured thread should work with most of the clamshells but some darker fabrics may require matching thread.
- Choose quite a busy background fabric rather than a solid, so it blends in with your clamshells. Sketchbook in Spring from Alchemy by Amy Butler was used for both background and backing fabric.
You Will Need
- Cotton fabric (66 pieces each – 3½in square – for the clamshells), 66 pieces
- Cotton fabric (15in square for the background)
- Fabric (2 pieces for the cushion back – 15in x 10in each)
- Card (3in square)
- Aluminium foil (About ½yd)
- Thread (Matching cotton thread)
- Perle cotton thread (No.8 in pink, orange and green (optional))
- 2 buttons, Optional
- Cushion pad (14in square)
- Basic quilting kit
- Sewing machine
Preparing the template
Copy the clamshell card template provided, cut it out and glue it to the 3in square of card. Carefully cut around the paper template so you have an exact card template.
Copy the clamshell fabric template provided and use it to cut out 66 clamshells from your printed fabrics.
Preparing the clamshells
Tear or cut a piece of aluminium foil about 5in square. Place one of your fabric clamshells right side down on to the foil square. Place your card template on top of the wrong side of the fabric (fig a).
Wrap the foil tightly around both fabric and template, pressing the foil down around the curved edge of the card template (fig b).
Using a steam iron on its highest setting, press this foil parcel on both sides (fig c and d). Leave to cool slightly.
Carefully open up the foil, release the fabric and remove the template. You should now have a perfectly turned over, curved seam (fig e). Press the curved seam again from both sides.
Take the background fabric and press a ½in seam around each side to give you a seam guideline.
With the right side up, place the top edge of the first clamshell on to the top left-hand corner of the background fabric and pin it in place within the seam guidelines (fig f).
Making the cushion cover
Using matching or neutral thread,sew the top curved edge of the clamshell to the background fabric (fig g). Use tiny, even stitches to catch the
curved edge of the clamshell and longer stitches behind.
Repeat steps 3–5 with your next piece of clamshell fabric, but re-using your foil piece from before. Pin the next pressed clamshell, right side up, next to the first clamshell (fig h). Use your card template to help space the clamshells accurately. Sew in place as before.
Repeat with another four clamshells until you have a full row of 6 clamshells (fig i).
Building the clamshell rows
Repeat the steps above for your next row of clamshells (fig j).
The first clamshell will overlap on the left-hand side. At this stage you might like to prepare a full row of clamshells at a time and pin in place before sewing. Use your card template as a guide for placing clamshells in each row. You can also use a ruler to line up your rows (fig k).
Continue adding one row after another until you have eleven rows (fig l). Press and then trim the overlapping clamshell fabric to the size of the background fabric.
Add some hand quilting before finishing your cushion. We quilted at the bottom of each clamshell in alternate rows of orange, pink and green.
Making up the cover
Take one of the pieces of cushion back fabric and turn over ½in twice on one of the long edges. Pin and then sew in place to hem. Repeat with one of the long edges on the other cushion back piece and then press. If you would like to add buttonholes to your cushion back do this now, otherwise you can just make an envelope opening without any fastenings.
Place the two back pieces on top of your cushion front, right sides together, overlapping the back pieces. If you have made buttonholes then these need to go next to the cushion front.
Pin and sew all around using a ½in seam. Snip corners, turn right side out and press. Sew on the buttons if you are using them. Insert the cushion pad to finish.
How to make a clamshell quilt
Want to use this technique to make a whole quilt? Good news – once you’ve got the hang of piecing your scallops with our clamshell template and instructions, simply use this method but on a larger scale to create a whole quilt top.
To turn it into a full-size quilt, check out our guide to quilting for beginners.