Stand about 10 feet away from a wall.
Pass the ball around your back so it bounces back on your front side. Once you catch the ball again, you wrap it around your back again and continue the drill in the same way.
Once you get used to it, try increase the speed or distance away from the wall.
Good team defence is five players guarding the ball, not five separate one-on-ones. The shell drill is where that starts, so here is how to teach help-side positioning and rotations from the first week of the season.
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.