The beauty of stone floors is they are more forgiving of uneven terrain.

You can also use the horizontal beams on the ground instead of wood floors. In all of my armory buildings now I set down horizontal beams to ck for evenness around the perimeter, put down first vertial support beams, set up doorways, to be sure they are blue then I use the paving as floors in those buildings and in portal hubs. Saves on both wood and stone and looks good. Then pave walkway to kitchen/sleeping building which ties it all together. And if you hate it, can easily just re-flatten.