Why was John Davis a multi-time World champion and record holder? One reason was that he took his squatting seriously. In fact, heavy squats have built the foundation of some of the greatest strength athletes in history.
Here's a look at the great John Davis squatting at Ed Yarick's Gym in Oakland, California in the 50's. That's 400 lbs. and he makes it look easy. No monkey business there, just pure power development.
I don't generally recommend squatting with a board under the heels but it seems to work for John Davis, who was Twice Olympic Weightlifting Champion (1948 and 1952) and Six Time Senior World Weightlifting Champion (1938, 1946, 1947, 1949, 1950, 1951).