squat form check You've got it mixed up. Squatting barefoot is the most natural and is the best, but not even mandatory. Flat soled is recommended because squatting on a flat surface is "better" then an elevated surface. Both are fantastic and both are the right way.
squat form check It may be natural, but a flat sole gives you much more stability, and by the looks of it that is what made him miss the lift, this is like running barefoot, sure its natural, buts its easier and more comfortable doing it in shoes. Shane just use any shoes, doesn't really matter to be honest, aslong as it has a decently hard sole and is flat, I lift in adidas superstars. Why don't you try using a belt, it really helps lol