Place your palms beside your head on raised surface, fingers pointing towards feet, with your body leaning back against the raised surface.
Push on the hands, straighten the elbows and push the hips up, smoothly arching the back one vertebrae at a time.
Pause at the top and then slowly reverse the movement.
This variation has greater flexibility requirement than doing the Bridge on the ground, but can be easier to perform from a strength perspective. Depending on your personal strengths and weaknesses, it can be used as lower or higher progression than the Bridge .
Risks
If you lose strength in the shoulders during the exercise, you might fall face first onto the platform, so do not go to failure.
Make sure the surface you are pushing on cannot slide.