When I was training (25 odd years ago) I was taught that the first thing g to hit the ground when diving should be the hip/butt area as it provides the most cushion. From there it would be arms and last the ball. Top leg knee should be bent up to protect the stomach and forearms protect the face. This is also the technique I teach when I coach. Lately I’ve seen a lot of people say the ball should hit the ground first as the ball will take the most of the impact. I see several issues with this:
1) causes an awkward bend in the body
2) due to the bend might not reach the upper corners
3) if you don’t catch the ball you come down on your hands putting the entire impact of the landing on your hands, wrists, elbows and shoulder