Once I got the benchwork completed, I made miniature stud walls from 3/4" plywood cut to 1" wide. I then screwed them to the benchwork from underneath, This way I could remove them after the back drop had been installed if I need to make any changes.
The back drop is 1/8" Masonite.
A few friends have used ceiling tile panels glued to the plywood sub roadbed. I took it a step further and glued down a layer of the 1-1/2" thick white foam board using PL300 so it wouldn't melt the foam. Then I glued the ceiling tile on top of the foam board.
This will give me enough room to carve out rivers, creeks, sloughs and depressions in the scenery without having to cut into the plywood base.
Once I had this was down, I started in on laying the cork and track.