Obtain a ticking fabric for a down-proof cover. The fabric should be tightly woven with thick thread. A tight weave prevents feather quills from poking through the fabric.
Unzip the cover on a seat cushion and pull out the down feather cushion insert. You may unpick the seam on one side of the cushion if it does not have a zipper. Measure the length and width of each side of the insert, such as the large flat panels and the narrow side panels. Add an allowance of 1-inch to each figure. Use the measurements to cut pieces from the ticking fabric.
Match the pieces and pin them together. Use the cushion insert as a guide so you can match them correctly. Hand-sew or machine-stitch the pieces. Ensure that you leave an allowance of a quarter inch for each seam. Leave one side open for the down feather cushion insert.
Stuff the cushion insert into the new ticking cover. Hand-stitch the open end of the cover closed. Place the form into the cushion cover and zip or sew it shut.
Repeat Steps 2 to 4 for the remaining seat cushions.