It's not about how high the box is. It's about how explosive you are from the ground.
Start at the bottom with the palms facing each other. Rotate on the way up so the palms are facing forward in the end position.
With the squat, you want to break from the knees and hips at the same time. This plyo drill can teach the correct movement pattern and fix bad patterns.
To get results from this exercise, you must build a stable base. One way to do that is with the bottom-up variation. Here's how to do it.
Make the unilateral RDL work even better. Pull your toe towards you.
Overhead squats will improve your regular back squat technique and patterning.