I found this gem at the Power and bulk forum.
Set the pins in the power rack so that they stop you in the bottom position of the squat. Pause the bar on the pins and then explode upwards.
I have taken the liberty of adapting the program to approximate percentages loosely based on Hubbard's numbers.
The original program calls for 3 sets of 5 reps, but Hubbard has later changed this to 5 sets of 3 reps. Do what you prefer.
Week 1:
3 sets of 5 reps @ 57,5% of your normal squat 1RM
Week 2:
3 sets of 5 reps @ 60%.
Week 3:
3 sets of 5 reps @ 62,5%.
Week 4:
3 sets of 5 reps @ 65%.
Week 5:
3 sets of 5 reps @ 67,5%.
Week 6:
3 sets of 5 reps @ 70%.
Hubbard says that after these 6 weeks your normal unequipped squat should be stronger.