I doesn't really matter if the machine is not level on the floor as the epoxy will level out like pouring water into a channel it will find it's own level. What is important is that you do not have any leeks in the moat I put a very thin bead of silicone all around the inside.
You will need it about 5mm thick. If you use MDF for the moat after the silicone you could put some Vaseline on the insides of the moat to stop the epoxy from sticking.