A friend and I made our larger ironing services with a piece of plywood, a few 1 x 1 boards, cotton batting, and cotton fabric. What we did was take the plywood and put the ironing board in the middle of it and traced the ironing board. We then attached the 1"x1" boards to frame the ironing board so that the plywood would sit on top of the it without sliding. Then we put 2 layers of cotton batting on the board (we used a spray adhesive so it would not move), then we put the fabric on top and stapled it down tight. Some people use the insulated batting like the kind you use in potholders, but we didn't think it was necessary since we used 100% cotton batting. (3 years later it still looks great.)
We bought a standard size of plywood then cut it in half and each made the ironing board. It is wide enough to iron the width of fabric and not to far to reach across when ironing.