I like to iron on a good size square of white freezer paper to my cotton topped ironing board. The shiny side sticks to the surface for quite a while. When the freezer paper gets looking grungy from the starch, I peel it off and iron on a clean square.
Another trick is to cut off the closed end (makes a tube) of a brown paper grocery sack to slip over the ironing board. This protects the board when using starch and you just replace it when necessary.