Two players stand on one side of the net attacking, while one player is on the other side and will be the blocker.
On the attacking side, a player overhand passes the ball to a team mate who sets it back to him to spike. The blocker jumps from a settled spot and blocks the attacked ball.
Have players keep hands high and legs a little bent before blocking. Hands should be put on the other side over the net during block attempt.
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.