Skip to the 7:43 mark here for a video demonstration.
The lateral squat assists us to move the hip properly within the frontal plane.
This is one of the more challenging drills for people to get but when mastered it greatly improves the functionality of your hip, which in turn increases relative mobility.
Drive through the heel or tripod foot contact.
Move slowly into new depth.
The drive upward is "forward through the hips" not "toward the other side".