Envelope pillow covers are almost as easy to make as a plain square pillow cover. The envelope flap allows the maker to add a complementary or contrasting colour fabric and various trims, buttons or tassels. The size and shape of the pillow can be altered as long as the length of the top edge of the flap is equal to the length of the top edge of the pillow.
Cut two square fabric pieces and two square pieces of fusible fleece or batting 48.75 cm by 48.75 cm (19.5 inches by 19.5 inches). Cut two triangles of fabric and one of fusible fleece 48.75 cm by 26.2 cm by 26.2 cm (19.5 inches by 10.5 inches by 10.5 inches).
Fuse the fleece to the backs of the two squares and one triangle piece following the instructions provided with the fleece. Usually this is done by pressing the wrong side of the fabric to the rough, fusible side of the fleece with an iron set to a low temperature with no steam.
Pin any cording or trim you would like to use to the right side (not the wrong side) of the shorter sides of the triangle piece that has the fleece attached. Arrange the cording or trim next to or parallel to the raw edge of the fabric. The 9 mm (5/8 inch) seam allowance will eat up some of the trim, so you will not want the edge of the trim exactly lined up with the edge of the fabric. If you are using a tassel, add it here, too. The string of the tassel should be pinned so that it will be caught in the stitching.
Place the triangles' right sides (not the wrong sides) together with the cording or trim and the tassel in between, and sew the shorter sides using a 9 mm (5/8 inch) seam allowance. Turn right-side-out and press.
Pin one side of the long edge of the triangle piece to one side of a square piece, keeping the other long triangle edge free. Stitch. Fold the second long triangle edge under 1.5 cm (5/8 inch), place it over the raw edges just sewn, and slipstitch. The slipstitch will catch the folded edge of the triangle and the layer underneath. Only tiny stitches will show on top and the longer edges will be hidden between the layers.
Pin the cording or trim to the right side of the other square along three edges, again placing the inside edge of the cording or trim next to or parallel to the raw edges of the fabric. Baste.
Pin the two squares together matching the uncorded edge of one and the flapped edge of the other. Baste and sew the three corded edges, right sides together, using a 1.5 cm (5/8 inch) seam allowance. Turn right-side-out and press.
Sew a snap to the point of the flap and the corresponding part of the pillow. Put the pillow form inside and snap the flap down.
If you prefer to put cording or trim around the flap only, you will need 3/4 metres (3/4 yard). Instead of using a snap on the point of the flap, you can substitute a button and buttonhole or hook-and-loop tape.