1.Place 2 linen fabric together (we used a length of 42 x 42 cm). Measure zipper length (30 cm) across the centre of the fabric. Mark at each end with pins. 
2.Sew seams on both sides of the markings with 1 cm seam allowance. 
3.Open the zipper. Place the zipper end (where zipper teeth start) in the opening of the fabric. Lay fabric edge so that it flushes with the edge of zipper fabric tape (both are 1 cm wide). 
4.Sew one side of the zipper onto the opening. Use your sewing machine zipper foot. When you have sewn about halfway along the length of the zipper, raise presser foot. Close zipper, passing the presser foot. Lower presser foot and sew to the end of the zipper. Sew the other side of the zipper in the same way. 
5.Continue sewing in a straight line at the ends. Press (at medium iron temperature). Then sew the remaining edges together. NB: The zipper must be open. Turn the cushion to the right side through the open zipper.
