I've done it.
I covered 3/4" plywood (18 x 48) with that "silver ironing board" fabric, mine had a sticky back. For extra measure I stapled the edges to the bottom. I just lay it on top of my ironing board.
I personally prefer the silvery fabric as it stays cleaner than cotton because it doesn't soak up the starch like cotton does. I can just wipe the top of mine with a damp cloth. With as much starch as I use, I'd be changing the cotton and batting every month.
When I need my regular ironing board I just take the big board off and lean it against the wall.