Partner holds the ball behind, with one hand underneath and lightly against the neck of the "catcher". When the ball is released the "catcher" claps their hands on front & reaches behind to catch the ball before it hits the floor

Reaction
Ball familiarisation
Ready Stance

The ball can be moved lower down the back.
Players can hold it at the back of their knees, calfs & achilles, releasing clapping in front and catching behind before the ball hits the floor