I have uploaded a video to YouTube demonstrating this Pre Yoga Exercise to my friend. It is a spontaneous Mini lesson without frills but you might find it useful. It is also on FaceBook. This is for my students who don't follow along on FaceBook. I also added in the Knee Exercise that we do frequently after the Clamshell demo
Here is the Link:
https://youtu.be/NuUvzOJ_z8I