Adding a balance challenge to booty-shaping squats will keep your hips, glutes, and abs firing the entire time.
How to do it: Stand tall with your feet slightly wider than hip-width apart. Keeping your chest lifted and maintaining a neutral spine, lower into a deep squat, reaching both arms to the floor (try to tap the ground if you can).
As you press up, shift your weight into your right leg as you bend your left knee and grab onto your shin with your left hand [as shown]. Hold for 1 count, release your leg, and return to start. That's one rep. Do 20 reps total, alternating sides each time.