Clean your porch glider cushions. Brush off loose dirt with a soft brush and wash both sides with a mixture of 1/4-cup mild soap in a gallon of tepid water. Let air dry.
Inspect the cushions for signs of mildew or other damage. Kill mildew with a solution of 1 cup bleach mixed in 1 gallon of water. Spray the solution on the mildew, scrub with a brush, rinse and let air dry.
Repair damage to the existing cover, if needed. Hand-stitch tears closed and patch small holes with a needle and thread.
Iron the fabric according to the manufacturer's instructions.
Lay two layers of fabric right sides together on a large flat surface. Place the glider cushion on the fabric.
Draw a line around the edge of the cushion. Draw a second line 1 inch plus half the thickness of the cushion outside the first line. For cushions less than 1 inch thick, do not add extra depth.
Pin the fabric together between the two lines and cut through both layers on the outer line.
Sew the fabric together using a 1/2-inch seam allowance. Leave two-thirds of the back edge open.
Turn the cushion cover right-side out through the opening and insert the cushion. Check for proper fit and mark adjustments, if necessary.
Remove the cushion cover and turn wrong side out again. Sew marked adjustments, if needed, and sew over the seam for added strength.
Sew a zigzag stitch close to the seam line to finish the edge. Trim the fabric close to the zigzag stitch. Do not trim the fabric across the opening.
Turn the cushion cover right side out and insert the cushion.
Fold 1 inch of fabric on both edges of the opening to the inside and hand stitch the opening closed. Alternatively, sew the hook side of the hook-and-loop fastening tape to the unfolded seam allowance on one side of the opening and the loop side to the folded seam allowance on the other side.