In pairs, one with a ball as a setter, the other approaches to the net and spikes.
Setter throws the ball high enough so that the spiker could approach with at least three steps and be comfortable hitting.
Shorten approach time by throwing the ball just after the spiker makes first step forward.
New hitters rarely miss because of their arm. They miss because of their feet. Build a reliable approach, then time it with your setter.
When your hitter gets stuffed, five teammates standing and watching is how you lose the point. Good attack coverage turns a blocked ball into a second swing.
Coaches spend hours correcting arms in serve receive when the real fault is almost always the feet. Fix the movement and the platform fixes itself.