I made my portable ironing surface with cotton duck. I stapled it on, then sprayed it with water and let it dry. It shrank nice and tight around the board. Duck is awesome because it has a nap and holds fabric still as you press/iron.
My personal feeling is you don't need 3 layers of batting. I find I get better results from a harder surface rather than a softer surface - unless you're pressing a lot of applique, in which case I prefer a fluffy towel underneath. YMMV.