Hollow-core doors, $19.99 each from Home Depot, made benchwork construction a breeze. I fastened the doors to a 1" pine ledgerboard along the walls and used knee braces for support. I designed my benchwork to be portable in case we ever have to move. The layout sections are simply lag-bolted together as shown in the photo.
The resulting benchwork is quite rigid and easily supports my body weight.
I used green foamboard insulation from Lowe's as a scenery base. I initially used three inches of foamboard, which resulted in a track height of 53" off the floor. Upon placing temporary track and structure mock-ups, I found that 53" was a tad too low for my taste. I added another 2" layer of foam to bring the benchwork height to 55". I'm 5' 10" and 55" is about armpit height. I tested operations again before permanently attaching the additional foam layer, just to make sure that I could manually uncouple cars anywhere on the layout. The resulting 5" foam base layer allows for plenty of scenery below track level.