HOW: Start by lying on your back with your knees bent. Engage your core by drawing your ribcage down. Slowly bring your shoulders and upper back away from the floor. Your goal is to rotate and lift your left shoulder towards your right knee. Then lower yourself and repeat by lifting your right shoulder towards your left knee.
FEEL: You should feel your core and abs working to lift your shoulders off the ground, especially the sides of your core in your obliques.
COMPENSATION: Keep the movement slow and controlled.