Start with a 12″ quilt block and three coordinating fabrics. You’ll need 1/2 yard of two fabrics, and 3/4 yard of the body fabric.
Cut from the background fabric (light green):
2 pieces: 12.5″ x 4.5″
1 piece 20.5 x 12.5″
Cut from the inner fabric (dark green):
1 piece: 13.5″ x 40.5″
Cut from the body fabric (royal blue):
1 piece: 18.5″ x 40.5″
Stitch the 12.5″ pieces to either side of the block.
Stitch the final background piece to the end of one of the 12.5″ pieces to make one long strip.
Place the inner strip on top of the block’s strip, right sides together. The inner strip should be 1″ wider.
Press the seam towards the inner strip.
Add a layer of topstitching. This will give the pillowcase a finished look, and give some extra stability to the edge.
Fold this piece in half, to make a long strip. Place the body piece inside – you may need to fold the body piece to make it fit. If your body fabric has a right side, the right side should be facing the quilt block piece.
Pin all three layers together – the body piece sandwiched between the top and bottom of the stitched together piece.
Stitch the seam. Turn the whole thing right side out through one of the holes on the side. Press flat.
Fold in half, RIGHT SIDE OUT. This will feel strange, but is the first step in making a French seam. Pin the two sides with raw edges.
Stitch with a scant 1/4″ seam. This means slightly less than a 1/4″ seam.
Turn the pillowcase WRONG side out. Finger-press the edges, and pin in place.
Stitch using a 3/8″ seam allowance.
Turn the pillow right-side-out, and you’re all done!
The French seams and extra stitching will keep your pillowcase from fraying even after many washes!