You can start by sitting on the hoop. Hold on to the top with one hand; if you’re going right, grip with the right hand facing backwards on the right side of the hoop. Tilt so you are sitting more sideways and place the left hand on the bottom bar right behind you. Straighten it out and push hard into it as you slowly slide sideways off the hoop until only your neck and head are resting on it. If you press hard into your bottom hand and your back/shoulders/neck to feel stable, you can let go with the top hand.
See video below for a demonstration (she gets into traditional amazon about 10 seconds in):
Different variations can be seen here: