The simplest one you said is that you have to rely on inertia to turn it over at once. Keep your head down first, and then lean forward by inertia.
If you practice backhand, it is recommended to contact the backhand first to get familiar with the feeling and then come back to the back flip.
I only dare to flip in front of the swimming pool now.
Doing sit-ups every day can practice waist and abdomen strength. At the same time, you can also exercise your flexibility and coordination. When you feel that you have some strength, you can practice handspring. You can also ask a friend to hold your waist and experience that feeling later. Don't run to the grass to start.
thank you