In the case of squatting, one can set the pins to the desired bottom position, with the bar left on the pins. The lifter then gets down and wedges herself under the bar, being sure to focus on a high level of tension in her body and a good weight balance in her feet. Only after all this feels correct does take a final breath before pushing her legs to stand, finishing by either racking the bar or lowering it back to the pins.
There is absolutely no momentum, stretch reflex, nor, if she racks the bar at the top, is there any eccentric part to this lift. All of which makes this extremely difficult. It’s a great way to develop strength out of the hole, prevent soreness (if she eliminates the eccentric motion), and build a calloused will.
Strengthen the legs and the mind will follow.