My big ironing boards have one layer of batting then canvas which I stretched.
I followed Sharon Schamber's "perfect pressing board" on Youtube.
I started with a small one like hers then applied the same idea to my big
boards. Then I made separate covers with canvas and sewed canvas
ribbons(?) middle and ends to tie them underneath. Easy to remove and wash.
If you make two covers then you always have one on your ironing board
while the other one is in the wash. I use a lot of starch so my covers
get washed quite often.