I really like this exercise. It's so simple and easy and great to use with athletes of all levels.

Start with a box that is a little above parallel. As you get better at the exercise, you can lower the height of the box. Standing on one leg, keep the other leg off the ground throughout the entire set. Reach back with your hips first, just like doing a normal squat. Be sure to keep most of your bodyweight back on your heel. Slowly lower yourself to the box, being sure to sit softly (don't plop on the box!) Pause for a second on the box, then pushing through your whole foot, using your glutes, hamstrings and quads, stand up. Remember to keep your other foot off the ground the whole time. Repeat for desired number of reps before switching to the other leg.

Remember to make it more challenging by lowering the box height. You can also hold a med ball or weight or wear a weight vest for added resistance.