6 Players with 2 balls. The Coach decides whether to start the practice going clockwise or anti-clockwise. If you are one of the two middle people (players 1 & 2) then you change with each other once you have passed a ball. If you are on one of the corners then once you have passed your ball you exchange places with the person on your diagonal, e.g. Player 4 exchanges with player 5.
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.