I use a rectangular piece of plexiglass (that I happened to own) on top of a rectangle of thin plywood, on top of my regular wide-ish ironing board. Everything is covered by two layers of white denim from JA. Nothing is tacked down, but the denim doesn't slide much. The denim is very grippy for pressing blocks. I do move around a bit on the board when pressing, as the plexi wants to push up temporarily when hot.

I looked at endless tutorials online before it finally occurred to me that the cover doesn't really need to be a close fit like a regular ironing board cover or even tacked down. I can flip either layer of the denim over if needed.

If I need to do garment ironing, I lift the whole setup off or (better) push it sideways a bit to clear a space on the original ironing board underneath.

I used a coupon from JA for so much off a single cut to get the denim insanely cheap. I was using it for temporary light-blocking curtains (it didn't work that well, IMO.) After taking the pieces down, I realized that all the ideas I had for white denim were white jeans (not happening) or a tent, so I was glad to find a use for some of them.

hugs,
charlotte

I made one about 5 years ago - maybe longer, that is the plywood version with 2 layers of cotton batting and and 2 layers of cotton fabric. (It was fabric that my friend already had and we were both making ours together at the same time.) Living in So. Cal. moisture isn't that big of an issue - and there has been no warping or bowing in the wood. Maybe I don't iron as much as you guys - my ironing board hasn't had a problem with dampness.