Not the ENTIRE board (snicker...) let's see... foamcore columns supporting the castle, along with foundation walls, then the rest of the map solid insulation foam, possibly double-stacked depending on thickness, with carved-out cave corridors courtesy of the hot-wire cutter...
Um, yeah, there's no help at this point...
...And sometimes, you've got to pick your battles and get crackin'...
(Back to Photoshop...We'll stick with the surface for now, possibly with some slight elevation changes...)