My husband made a "big board" that fits on top of my existing ironing board...I've not taken it off since he made it! There are alot of tutorials on how to make one on this board and also on the internet. We made ours of plywood (I think 1/2" think) and it is heavy....so make sure your ironing board is stable. I covered mine with aluminum foil, then 2 layers of warm & natural batting and then covered it with that ironing-board fabric (silver) and then, I found a remnant of canvas and just laid on top and secured with those welding clips. (Someday I'll sew elastic on that so it stays). The canvas is kind of nice because it seems to "hold" the fabric when you are pressing pieces and blocks.
Good luck with whatever you do.....just check out the tutorials and then decide what would work for you.
My husband added some "stops" underneath so the board would not slip sideways and also so it would not slip backwards off the ironing board. We made it the full length of the board.