Box squatting can be a way to improve your CrossFitting abilities by increasing your posterior chain strength. This powerlifting type of squatting enables you to engage the glutes and hamstrings a little more than with a traditional squat because of it’s emphasis on the hip. It can provide a variation for Olympic lifting training if an individual is struggling with overuse of the knee especially when feeling discomfort at the knee catching the bounce out of the hole. This can also be a variation for individuals with limited ankle mobility; although, I would still encourage those with ankle mobility restrictions to work on full depth traditional squatting. Because this method of squatting is eliminating the momentum commonly used out of the hole, it works for developing power at potential sticking points in the squat.
Key points of position:
-neutral spine (not over arched back but also not rounded)
-keep core engaged
-toes slightly angled out with a wider stance than normal squat position
-vertical shins through the entire movement
-sit back and drive knees out
-sit soft while maintaining tight core
-transfer bodyweight to box with sitting and bring torso to slightly more vertical position
-only go to depth that you can control your descent
Have fun with it and happy squatting!