I've spent a lot of time scratching my chin on this one as well. I just bought some good boots and wool socks, and use a couple anti-fatigue mats that I scored from work (those work great, by the way). But I still might make a floor for my Base Camp.
My sled is 20" wide by 44" long. I need something that will fold up to fit on that. I was thinking that three pieces of plywood, hinged along the long side to fold accordion style, would work. It would be 60" by 44". That way, enough of the floor is exposed that I can park my sled (with all my equipment and a seat) in the Base Camp (its floor area is 72" by 72"), and have room around the edges for some holes.
Sounds like a lot of work to make more stuff to haul around, though.