Ensure the player's shooting arm has the elbow at approximately 90 degrees underneath the ball.
The wrist should be cocked back underneath the ball.
The non shooting hand should only be used as a guide to stabilise the ball.
Teach this skill to players individually, getting them to throw the ball in the air to themselves.
Once your players are used to this movement they can start to work in pairs, shooting at the basket.
Rebounding is the least glamorous thing in basketball and one of the most decisive. It is also almost entirely a habit, which means it is entirely coachable.
Good spacing is only the start. The best modern offences teach players to attack the defence's rotations and play in a permanent 4-on-3 - here is how to coach that read.
The ball screen produces almost half of all professional offensive possessions, yet most teams still teach it as a memorised play. The modern approach trains the read - giving players a framework to decide based on what the defence does, not what the coach called.