Starting in the centre of the court, players stand in a row behind each other facing the net.
On the coach's signal the players shuffle right and left. Every time they reach an axis or sideline they must bend and touch the floor with both hands.
Do not allow your players to lose contact with the floor, at least one of their feet must be touching at all times to ensure their reactions and acceleration are quicker.
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.