Start by standing on one leg, with the toes pointed forward and/or slightly turned out. Find a bar, bench or something similar so you can hold on to it with one hand.
With the front leg flexed and the foot pointed in front of you, active the core and hip flexors to prime the movement.
With the weight distributed in the foot that in on the ground, slowly sit down into a squat, making sure that the torso has a slight forward lean (similar to the back squat).
Once you have assumed a deep squat position, use your single leg strength to press towards into the floor, locking the core tight to allow to maximal effort.
Progressions And Regressions