Use loose Dacron to fill cushion corners before inserting the foam cushion to help keep the cushion corners looking plump, instead of wrinkly. Simply insert a small bit of Dacron (or polyester fiberfill, if you don’t have Dacron) into the cushion corners. Once the cushion is inserted, use a long needle (found at upholstery workroom supply stores or at craft departments in sewing or fabric stores) to move the loose Dacron or fiberfill around, so that there aren’t any lumps. Dacron is a material that is used to wrap foam cushions to make the cushions plumper, round out the cushion corners, and fill out fabric cushion covers as the fabric stretches and the foam compresses. But using this simple method, your cushion corners will look professional and smooth.