Do you need to use supports on flat models?

Hey everyone,This is my first post on here so please be nice. I'm relatively new to the 3D printing hobby so just getting to grips with some of the aspects of it so sorry if this is a bit of a stupid question? I'm currently printing on the Elegoo Mars 2 PRO and I'm trying to print some base stands to display some of my air soft pistols. The base plates are around 105mm x 40mm x 7mm thick but I'm not sure if its best to print these types of objects directly from the build plate or I should use supports? With the bases been quite big and flat will this cause an issue with suction if I never used supports?I've actually printed this without supports but the whole base ended up warping slightly and the top of the base that was the last layers to print, had a few dents on the surface and it had one little hole as well. I also did one with supports but I found this to sag a little and it also took 8 hours to print compared to 1 hr 50 without supports. I suppose my questions would be, which is the best way to print something that is a blocky shape and what's the reason for the dents on the surface? Any help and guidance will be hugely appreciated,Thank you