Re: Cover New Deck With Mat?
Large voids can be filled, the smaller imperfections will be hidden by the glass (mat or cloth), plus you'll need some kind of non skid surface (Gel coat, carpet, paint, vinyl) over the glass. whatever you use will hide more uneveness, applying a webbed or splatter finish will hide even more stuff.
All sides of the plywood should be sealed, and pre coat all the wood with resin before doing any glass work, if you don't the wood can suck resin out of the glass and leave dry spots.