Measure the diameter of the inside of your rim. Draw a circle on your plywood using your compass so it equals the measurement of the rims inside. Cut along the line using your jigsaw.
Set your circular piece of plywood on the foam and use it as a stencil to cut out a circular piece of foam that has the same diameter. Use your foam cutter.
Lay your upholstery fabric flat. It must measure equal the diameter plus 13 inches in area. Set the foam on the upholstery so it is centered and set the plywood on top of the foam. Fold the fabric over the plywood and staple it down using a staple for every inch. This is your rim seat pad.
Set your rim seat pad into the rim. This is seat is now ready for use.