I put up some temp card board to cover the under layout. But I wanted something more to make the layout 3-D
Before:
I knew I would need a kick board to keep the scenery nice so I used cut 1x3's and screwed them to the 2x2 support post...
Then I started the foam... this was a big job and took along time...
and the mess and the foam and more foam... and more foam...