HOW: Place a slider under the leg you do NOT want to work. The working leg is the leg that does not move. Slowly lower your body into a partial squat. Then slide the slider in front of you and make a complete circle without losing your partial squat position.
FEEL: You should feel all the muscles, especially your quadriceps and glutes, in your stationary leg working to maintain your balance.
COMPENSATION: Do not put too much weight through the slider! Pretend there is an eggshell under your foot.