Today I remedied this by mixing up a batch of epoxy and giving the ply a good coat. You could use paint or poly, or whatever. I use epoxy for my other hobby Wood boat building so I went with that. Whipped up a 6 oz batch and liberally painted it on. Once it's dry it will be ready for use again.
A few notes on the board. You need to Countersink your bolt heads so the board sits flush on the surface you are going to mount it too so take that in to account when determining the thickness of wood to use. Make the board as wide as the surface you intend to clamp it too. My counter doesn't have a lip big enough on the end I put the board on so I have to clamp at the ends of the board.