Remove the upholstery from the ottoman using pliers, a flat screwdriver and a claw hammer. Be careful not to rip the fabric. Remove the fastener from the underside of prong-type buttons, and unbend the prongs to pull the buttons from the top. Take pictures or make sketches of how the pieces go together to help you when installing the new upholstery.
Separate the fabric pieces using a seam ripper. Iron out the pieces so that they are flat. Label each piece so that you know how they fit together.
Pin the fabric pieces to the new decorator fabric, and cut out the new pieces. Sew the pieces right sides together following the pattern, sketches and photos you used when removing the cover. Sew using a 1/2-inch seam allowance. Double stitch seams that are in areas that are used a lot. Double stitching is to stitch over the same seam twice.
Turn the cover right side out and place it over the ottoman. Often the pillow top cover is attached separate from the bottom skirt. Attach the top pillow cover over the pillow to the underside of the ottoman support board and staple in place. Most skirts are attached with staples and a staple gun by inverting the already-covered pillow and stapling the skirt top close to the underside edge of the support board over the top upholstery fabric.
Glue trim or welting around the seam between the top and bottom covers. Cover buttons for tufting by cutting a circle of fabric twice the size of the button. Place the fabric face side down. Place the top piece of the covered button top side down. Press the fabric to the underside and into the teeth. Press the bottom part of the button into the top part until they snap together.
Thread a long upholstery needle with heavy-duty thread. Tie the loose ends of the thread to a flat four-hole button. Slide the needle up through the drilled hole in the underside support wood. Keep the needle level and straight through the foam and out through the fabric.
Thread the needle through the stem of the covered button, back through the hole in the support wood and through a hole in the first button. Pull snug so that the covered button tufts in the foam of the ottoman. Send the needle back and forth through both buttons three or four times, and tie the thread off at a button. Repeat for each button.