Lower the bar down to the knees, as if you were doing a Romanian deadlift.
Explode into a vertical jump while holding the bar. Do not pull the bar. The arms stay straight.
Don't lower the bar too slowly. Just keep it under control. Be sure to finish the hip extension; make yourself "tall." Don't be surprised if you jump backward a bit when you get it right.
Sometimes I think that I've been coaching and training so long that I just take for granted this thing called "experience". As an athlete, I always felt that w? wasted up to an hour of practice doing this thing called a "warm-up".