To make a pillowcase out of fabric, you'll need a piece of fabric that's at least 20” long and 18” wide. Cut the fabric into two equal pieces, then unfold and lay each one flat. With right sides together, sew along the short edge, pivoting as you go to prevent stretching (skipping steps will result in a poor seam). Turn the pillowcase right side out, topstitch around the opening, and press well.