Making your own padded bench seat has many pros. For one, you are ensuring that the seat will be the perfect size and shape for your bench. You'll also be able to choose your own fabric, leaving endless customisation options. Even if you don't have a sewing machine or know how to use one, bench cushions are simple enough to be sewn by hand, leaving no need for extensive sewing experience.
Cut a piece of foam padding, found in craft stores or online, into the unique size and shape that is needed to cover the bench with a pair of heavy-duty craft scissors.
Lay the padding over a double layer of the fabric of your choice, with the patterned sides facing inward. Cut around the padding, giving an extra 1 inch on each side to allow room for the seams.
Thread a sewing needle with thread that matches the fabric. Make sure to use enough thread to go around the entire fabric cut out, plus another 6 inches or so.
Sew the perimeter of the inside-out cushion cover together, keeping your stitches consistent in size and about 1/2 inch away from the edge of the fabric. Stop and knot the end when there is about 4 inches left to sew.
Turn the cushion cover right side out through the 4-inch opening. Use a yardstick to poke any corners out and stuff the foam padding inside. Move the padding around to where it's supposed to fit using the yardstick and your hands.
Knot the ends of the leftover thread that is still on the needle and sew the remaining 4 inches shut with the padding inside. Knot the thread and cut away any excess thread and the needle with the scissors.