I sometimes want to place a planter box or hot tub or swim spa cut into a deck or floor.
Without having to search around for some 3D depiction of what I want often it is easier to just create a solid cube or similar
to drop down into the deck. However, that just leaves a flat top on the cube and does not reasonably depict the hollowed
out part of a box, tub or spa. How would I best best create that hollowed out ( or depressed ) part, so a 3D looks a little
more like it should ?