"The pick up and underarm throw is a straight forward skill when you know the correct technique. The key to executing the skill well is to attack the ball and stay as low as possible on the approach.
Pick the ball up next to your right foot if you are right handed and your left foot if you are left handed. When you have picked the ball, up with your next step release the ball with your hand going towards your target.
As you can see from the clip, the pick up and throw is done in one motion. Which saves time and gives you power in the throw."