The grasping of the ball is important, and the correct way improves the ability to throw the ball correct and precise. That goes for every possible way of throwing the ball.
The hand is spread as much as possible in such a way, that the thumb and little finger don't loose a firm grip of the ball, as it is those two fingers, who direct the ball in the intended direction. The 3 middle fingers are slightly spread, so that they can give the ball extra speed at the moment of shooting by giving it the last flick. The ball must only be in contact with the outside of the palm.
The most ordinary errors are, that the distance between the thumb and the little finger is too small or the ball is in full contact with the palm.
Exercises to hold (and catch) the ball is throwing it to the floor and catch it again with one hand. The palm must be turned downwards.