Sit on the ground with your knees bent and your heels about a foot from your bum.
Lean slightly back without rounding your spine at all. It is really important and difficult to keep your back straight, but don't let it curve. If you can do this, try lifting your heels to increase the difficulty of the move.
Place your arms straight out in front of you with your palms touching. Your hands should be level with the bottom of your rib cage.
Pull your navel to your spine, and twist slowly to the left. The movement is not large and comes from the ribs rotating, not from your arms swinging. Inhale through centre, and rotate to the right. This completes one rep.