Elevating the heels kind of defeats the purpose. I think it would be better to just not go all the way down. The goal isn’t to get your butt down, it’s to improve ankle and hip mobility so you can get your butt down. Hold on to something or, like I’ve been doing it lately, squat with your back against the wall. When I start out I can’t even get close to getting into the squat position. After a minute or so I can finally get into the low squat position and after a couple more minutes I can start pushing the knees out. You can also try with your feet farther apart and progress by bringing them closer together .The main thing to remember is to not let the knees track to the inside of the big toes.