I use a manta ray for assistance. I can do lighter weights without it, but once I go close to max, I need t because my shoulder isnt good enough yet. I have heard boards under the heels are bad, something about the stress on the knees. But I squat in bare feet, or wear some chucks if it is a max day for support. I never wear shoes tho, luckily, Ive never had an accident in the home gym, with the exception of stubbing toes. Oh, box squats are fun.
if doing calves, you can use the board/block for a step off, get the mad stretch in the calves.