Split into groups of 4 and put them at different baskets. They will take 1 shot with correct form get the rebound and then pass it back to the next person in line.
Focus on correct form.
A lot of positive reinforcement to the players. Let them know when they have done a great shot.
We are not focusing on makes and misses, however if you want to here you can put players into different teams and have a shooting competition.
Play first team to 5 baskets.
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.