The coach is halfway between the service line and the net with a basket of balls ready. Two players are on the same side of the court with the coach, with no racquets (they are the “fielders”). On the other side of the net, at the baseline, the rest of the players form two lines. 
The coach will double-feed, one ball to the first player in each line. They will execute groundstrokes hitting them over the net. If they miss the ball, they get another one.
The fielders will try to catch 3 balls that come to their side. They can catch them off the air or after one bounce. Once one of them catches three balls, he/she replaces the player whose ball they caught last.