This is a great way to blast the legs without loading the spine. You'll need a cable station and a belt. Attach the belt to a low cable, walk back about ten feet, and start squatting. It's easy to do alone, there's no need to stand on risers, and you can choose whatever stance width is most comfortable for you.
You have to consciously grip the floor with your toes and push back throughout the set to keep from getting pulled back in by the cable, which keeps constant tension on the quads, even at the top of the rep.
Think about how much reverse sled drags burn your quads from pushing backwards; you're essentially doing that throughout the movement, plus squatting. It's a full-on quad assault! The cable also helps ingrain good squatting technique because you have to keep an upright torso with your weight on your heels or else you'll lose balance and fall forward.