I'm assuming you're going to add some modest undulation to the land. Typically I like to permanently install a foundation that rises above the ground a couple of scale feet, then I add tabs that hold the building in place. I use micro plugs for the wiring, so the female end is in the "basement", and the building simply gets plugged in, and set in place over the nesting tabs.
If you run the tabs the full length of the foundation wall and paint them black, there's no light leaks, or, if you use a floor to build an interior, you can use posts at the corners rather than tabs to hold the building in place.
If the object of the game is to remove the structures to stow them so you can take the modules safely to a show, this method works well. You can landscape right up to the foundation, and everything looks permanently mounted when it's set up. You can also permanently install things like steps to the landscape and such that would be more fragile if they're hanging off the sides of the buildings.
Lee