Flat Foot Squat

There are a couple things you can try as you start to build your mobility.

You can squat to a solid surface like a high coffee table that allows you to keep your weight on your heels all the way down, until your butt is on the surface. Lightly touch down and then press back up through mid foot.

You can also use Lunges instead of 1 legged squats, going only as low as you can while maintaining good form.