The bottom was printed with no supports, at least during printing. It was divided into flat panels for all the surfaces and then glued together. There is a fair amount of internal bracing to keep it from sagging. The size is slightly bigger than 2' x 2.5'.
The printer is one I designed and built myself. I actually built two of them because I knew people would want me to print stuff and I wanted to have one dedicated to the models I'm building.

The build volume is 400mm x 300mm x 300mm or about 15.5" x 11.5" x 11.5". After my most recent update I can print draft mode at 200mm/sec and finish parts at 75mm to 100mm/sec.