To do the Oblique Crunches, lie on your back and bend your knees to place your feet flat on the ground. Then let your knees drop to one side and your feet come up. You may need to adjust positioning slightly and move your knees and feet a bit further away or closer to your body depending on your flexibility.
Then with your knees down toward one side, place your hands behind your head. Rest your head in your hands with a space between your chin and your chest. Keep your neck relaxed and don’t tuck your chin into your chest.
Crunch up, lifting your shoulder blades up as high as you can while keeping your knees relaxed down toward one side.
As you crunch up, do not tuck your chin, but feel your abs working to lift your shoulder blades up. Lower back down and repeat. You can even put one hand on the opposite side from your knees to feel your abs working as you crunch.
Complete all reps then lower your knees down toward the other side.