I always point to Alpha destiny’s novice program. That and ICF. I had great gains doing Alpha’s program. It cover alot of posterior work (box squats, Stiff legged deads and even weighted planks. The majority of people’s problems squatting is lack of posterior chain strength. That’s why you barely see ppl go below parallel and when they do they drive their knees forward.
PRO TIP. Breaths through your mouth. “Eat” the air and fill your core with air. This will make your Squats more explosive