You should have enough room behind the flange of the dishwasher to use a piece of 1/2" all thread rod and a couple of wall plates which is what would mount to the floor and top ( may have to alter the plates some to keep them from sticking out. I would also check and see if that style of dishwasher would allow you to push a piece of 1/2" plywood up against it and then screw it to the top and floor.