Seated squats have been used for years and have been heavily popularized by Louie Simmons (American powerlifter). This variant of the squat requires that you control the descent phase of your squat, you stop completely by sitting down (while keeping a good posture) and return to the starting position.
The squat box is very interesting because it requires focusing on both a static and dynamic effort. For practitioners who have difficulty getting up from a squat with a large amplitude, this method allows to specifically work this transition zone at Crossfit in Texas.
The squat 1 + 1/4 is an excellent variant of the classic squat that also increases its performance in low flexion. This squat requires that you make a normal descent, go back up, then arrive at about 1/4 of the ascent, go down again and go back up completely.