Butterfly Leg Raise
To do Butterfly Leg Raises, lie on your back with your hands behind your head or down by your sides. Bring your heels together and let your knees fall open. You can bring your heels in toward your butt more if you are more flexible, but focus more on keeping the knees open and heels together. You can even keep the entire inside of your feet together if possible.
Press your low back into the ground and brace your abs. Then lift your heels up, keeping your knees wide as you lift your legs up toward the ceiling, lifting your butt up off the ground at the top. Lower back down and repeat, keeping your knees apart the entire time.
You can make the move more challenging, but also help yourself engage your abs harder by lifting your upper body and holding in that crunch position.