Benchwork looks good. If the flat areas need to support only lightweight scenery and structures, you might consider extruded pink foam for the base.
Picture shows the north end of my 10'-by-5' layout. There is a 1/2-inch plywood base topped by 1-inch layers of extruded pink foam. Except for the bridges, the track is laid on cork roadbed glued to the foam. Extruded pink foam is not messy to work with and can be stacked and easily carved to make lightweight scenery.
MELGAR
