Players face the net, with their arms in front of them controlling the ball. Players jump up and reach over the net before dropping the ball. The challenge is for the players to catch the ball while landing before it hits the floor.
If players are too small to handle it, lower the net a little. They need to control their jump so they don't fly forward or sideways.
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.