Unzip the cushion and remove any old stuffing. Or you can add to the existing stuffing, thus reducing the amount of new stuffing you’ll need to purchase.
Grab a handful of stuffing from the fiberfill package. Put the stuffing through the zipper opening and into the cushion, pushing it to the farthest edge and into the corners.
Continue stuffing the cushion with the fiberfill until the cushion reaches the desired thickness. Zip the cushion closed and replace onto the couch.
Turn the cushion so you are looking at the back seam. Use the seam ripper to cut a 5-inch opening along the back seam by inserting the seam ripper under a stitch, then pushing the seam ripper until the middle “hook” cutter touches the seam and cuts it. Continue sliding the seam ripper under the stitches until the 5-inch opening is formed.
Remove any old stuffing by placing your hand through the opening and pulling out the stuffing inside. Disregard this step if you are adding to the existing stuffing rather than replacing all of the former stuffing.
Grab a handful of new polyester fiberfill stuffing from the package and put it through the opening in the cushion, pushing it into the corners and to the farthest edge of the cushion cover. Continue stuffing until the cushion reaches the desired thickness.
Use the needle and thread to sew closed the 5-inch opening along the back seam of the couch cushion using a whipstitch.