A back squat cue is: ‘HIPS BACK’.
Note the difference ー for the front squat, the cue is HIPS DOWN. The back squat has better leverage, so the hips can go farther back, optimally engaging the glutes & hams. This helps move the load from a solid foot position, rather than from the toes.
Do NOT squat on your toes. Tendons are weak, bones are strong.
Hips-back brings more of the posterior chain into the movement, so more weight can be lifted than with the (poor-leverage) front squat.
This will cause the shoulders and upper back to be active, so the bar stays put.