Stand in front of a weight bench or box in the gym that is around knee height, facing away. Balance on one foot and extend the other in front, then slowly descend with control in a single-leg squat until you touch the box. Touch as lightly as possible, then use the strength of the balancing leg to stand back up again.
This is a great option to challenge strength through range of motion with minimal equipment. Even if you also do weighted squats, I recommend including this high-level bodyweight move as well.