As always when people are struggling to learn the full squat, I suggest zombie squats with either an empty bar or a lighter broomstick or something (front squat with arms out in front).
Try them for an hour and I bet you'll get damn close to a perfect full squat. If not, start with aggressive mobility work and high rep leg press for the first few weeks, then try again.
Also, include some kind of glute activation before you squat (glute bridges would be ideal), and remember the golden rule of lifting: hold your breath and get TIGHT by pushing your abs out and ribcage down.
Best of luck!