Re: Garage Gym peeps...help! Advice sought..
Couple of ways to go on this. I didn't do anything to level my platform, but mine was turned sideways from the grading. On squats it would feel like one leg was shorter than the other, but I just dealt with it. If it rolls, you can just put a lip on the edge of the platform to keep the bar from rolling off it, most people keep hold of the barbell while setting up for a lift.
The main way I've seen people level their platform is to use thin plywood, like 1/8" and cut a few pieces at different lengths to even out the grading. To me, this seems like too much work, but that's just me.