Select from:
[+] If you are lying on your back, you may want to sit in a small chair. Try to hold your core muscles when you do this..
[+] Raise yourself up into the starting position, keeping your back flat. If you've never tried a backbend/vault, try variations of..
[+] As you get more comfortable with this move, you can start from a standing squat. Eventually you will start from a completely standing position..
[+] Put your feet on the floor at chest level, as if you were about to walk over to your bed. Take a few steps forward with your right foot..Choose from options above and answer: What most naturally follows?

How to do a back extension
Start in a squatting position.
Bend your knees and come close to the floor, almost as though you are going to sit. Hover just above the ground, with your thighs hugging close to your calves.
Answer:
As you get more comfortable with this move, you can start from a standing squat. Eventually you will start from a completely standing position.