The goal here is to rotate your spine by contracting the muscles around your midsection. On the side that your knee is bent, think of lifting your pelvis up and over as you rotate. Keep the opposite side shoulder down on the floor as you rotate; if your spinning left your right shoulder needs to stay down. Do not create a big stretch; only go as far as you are still actively generating tension from your midsection. Be completely solid and still at the end of your rotation; hold the position long enough to feel stable and locked in, then return down slowly with control.