Sit on the ground with your knees bent and your heels about a foot from your butt.
Slowly recline backward a few inches without rounding your spine.
Place your hands out in front of you (you can hold them in front of your chest).
Pull your navel to your spine, and twist slowly to the right. The movement is not large and comes from your ribs rotating, not from your arms swinging.
Come back to center, and rotate to the left.
This counts as one rep. Keep alternating for 30 seconds.