If the ball is going diagonally it must be thrown underarm. If the ball is being thrown along one of the edges it must be rolled (flat or bobble feed).
Players can choose where they throw the ball - they can either roll it square along the floor or they can throw the ball diagonally in the air.
Approach the ball at pace, get low, stay low, practice quick release.
The underarm throw should be accurate and the receiving player shouldn't have to take more than one step to catch the ball.
The bobble feed should be made a pace to challenge the receiving players' ball-stopping skills.