Take a pillowcase apart at the seams, using a seam ripper. This creates two rectangles of fabric.
Measure the width of the pillow, which is the shortest side, using a measuring tape.
Determine the width that you want the border to be, adding 1 inch to this measurement.
Cut two rectangles that match the measurements in Steps 2 and 3 from the fabric you want to use as the border, using a pair of scissors.
Fold one long edge of the fabric rectangles down toward the wrong side, creating a fold that is 1-inch deep.
Iron the fold flat.
Place one rectangle down on the right side of one of the rectangles from the pillow case, lining it up so it will border the end of the pillow that is sewn closed. The ironed edge should be placed on the pillowcase, while the unfinished edges line up with the edges of the pillow case.
Pin the rectangle in place.
Sew a line along the folded edge using a sewing machine, securing it to the pillow case.
Repeat Steps 7 through 9 for the other rectangle of fabric.
Place the two sides of the pillowcase together, pattern side in.
Sew the two sides of the pillowcase together again by running a seam along the raw edges with a sewing machine.
Turn the pillowcase right side out. It is now ready to be used.