In pairs facing each other, players throw the ball two handed overhead and into the ground, bending the body correctly. The ball should then bounce up and reach the other player.
Blocking requires strained muscles of abdomen and back, and in this drill they work sufficiently.
Progression may be applied by standing backwards to teammate and throwing the ball without looking.
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.