To make a standard pillowcase:
1. Cut two identical pieces of fabric 29.5 inches long by 21 inches wide.
2. Fold over 3.5 inches on one long end of each fabric piece and iron it down to create a cuff. Sew this folded edge to itself.
3. With right sides together, line up the cuffs and pin the remaining three sides, leaving the cuffs open. Sew around the three pinned sides to complete the pillowcase.