Measure the amount of piping and fabric you'll need and add four to six inches. You'll need to cut long strips of fabric on the bias. The width will depend on the size of the piping. For the piping I selected, I cut strips two and a half inches wide. This gives me about a one inch allowance when the piping is placed inside the strip. Stitch the strips together.
(Psst...I didn't cut on the bias. But you should. It's the correct way to make piping.)
Using a zipper foot, stitch close to the piping folded inside the fabric. If your sewing machine has a side-to-side needle adjustment, you may need to move the needle a little to the left to get the stitch snug against the piping.
Attach the piping to body of the ottoman, stapling along the seam of the piping and leaving about two inches loose on each end of the piping. You may find that you need to cut little notches in the fabric when you reach the corners so the piping will lay flat, but don't snip through the stitching.
Mark where the two ends of the piping overlap.
Carefully rip the seam on one end of the piping to expose the cord inside. Snip the excess cord so it evenly meets the other end. Only cut the piping! Don't cut the fabric.
Fold the loose flap of fabric, leaving about three-quarters of an inch to hang over the end of the piping you just trimmed. Tuck the opposite end of the cording inside and tack into place.
That's all there is to it! If you can draw a straight line, cut a straight line and sew a straight line, you can build and trim your own ottoman.