The pause squat can be used as either back squat or front squat. It places more emphasis on the bottom range of the squat and the drive out of the hole, therefore improving the rate of force development.
Set up in either the back squat or front squat and perform the eccentric portion of the lift as per normal. Once the bottom position is reached pause for the prescribed amount of time, ensuring tension is maintained throughout and no bouncing or movement takes place. On completion of the pause drive back up aggressively making sure you drive the shoulders up into the bar and lead the movement with the chest.
Pause squats have few main benefits. A pause of 3-4 seconds will help improve the rate of force development by eliminating the stretch shortening cycle. Longer pauses can be held and will help strengthen the trunk and positions at the bottom of the lift as well as flexibility of the hips, ankles and upper back.. Pause squats will also help address and technical flaws such as leading with the hips
Pause squats can be used much like any other squat, however, the number of reps prescribed will depend on the length of the pause. I rarely recommend reps in excess of 5 and my go to pause is 3 seconds. I do however like to use longer pauses on lighter days, this helps keep the load down and will aid mobility following a heavy day.