In gymnastics or cheerleading when you're tumbling a big skill that's fun to show off is something called a back tuck, a.k.a. back flip. This is actually a very difficult skill to do and it takes a lot of practice and it needs to be done precisely. It's very easy to get injured; not flipping enough or landing too low can cause some ankle issues or even landing on your head.
So in order to do this you need to focus on how it is not so much throwing backwards as it is rotating your hips over your head. Working on really bending down and jumping up as high as you can, swinging your arms. And you do want to jump back at a slight angle, not to throw your head back, not to throw an arch, but just to stretch at an angle and then lift your knees and hips aggressively over the top of your head.
This does take a lot of practice, it does take a lot of strength, and it a lot of time to achieve. But ultimately there are some drills you can do that are very simple in order to achieve this really cool little skill you can show your friends.