Players work in pairs and face each other, moving sideways along the court. While moving, players keep their knees bent and throw the ball underhand to each other.
This exercise requires strong footwork and proper defense position; ball throws imitates digging.
You may introduce a second ball to have players make steps faster.
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.