Sit Up Crunches - lay on back, do a normal crunch, but
reach your right hand to your right foot, keep core strong, you will be turning towards your feet for each repetition, and then stable your body up in the centre before laying back, and doing it again.
You can also do this same exercise with more intensity, by laying on your side on your bed with your torso hanging off the bed. Then use your core strength to lift your torso sideways, upwards to your hip as far as you can.