Fold the fabric in two and measure a rectangle that is 34 by 49.5 inches. Cut out the rectangle and place it on an iron-safe surface with the pattern facing down.
Fold all the edges in 1/4 inch and press with an iron so the edges are crisp. Fold the edges in again by 1/2 inch and press.
Run a line of double-sided fusible interfacing under the last fold and iron it into place. Make sure that the iron's steam setting is on, as the webbing requires moisture and heat to from a bond. Now the edges of the cover are hemmed and won't unravel.
Fold the cover in two with the pattern on the outside.
Mark snap locations along both sides of the fabric all the way around the cover. The snaps should be spaced every 4 inches, and the marks should match exactly on the two pieces of the cover.
Poke a hole into each marked space with an awl and position the snap. Make sure the mate of the snap is on the other side of the cover. Place the snap with the smooth side facing out and the snap side on the inside of the cover. Repeat all the way around the cover.