High balls. Easy.
Like a forehand swing, throw your racquet high enough and over the fence.
When youre throwing the racquet, its not an arming stroke, as long as you start with the butt directed at the ball on takeback. Let the racquet and the handle throw themselves up to the ball. Relax wrist relax. To ensure relax wrist on this particular shot, pull your grip further the end of the handle.