I might construct this in two halves, using two 4x8 sheets of 2" thick foam. Divided along the vertical blue line. With a cut-out in the left section for the tree stand. Easy to set-up and take-down, light for carrying, and to store between seasons. Use left-over sections of the foam sheets to build up the elevated interior. Use a foam-safe white paint (latex?).
The track can be permanently attached to the base sections. Lighted Christmas village buildings are removable.
Carve a channel on the underside of the left sheet foam, to run from the top above the crossing, to the tree-stand interior area, for power cords for the tree lights, village buildings, and to the track.
I would use Woodland Scenics foam inclines at 3% for the grades, to get a smooth grade without measuring and calculating. The entire slope on each half, runs entirely on that half, so the slopes do not break across a section, but run continuously on that half of the layout.
