Volley the ball to your partner who digs the ball to themselves then volleys the ball back to you, whilst they are doing that you do a dive, roll or something else then they do the same as you dig and volley. Do this for a set time or number of good contacts.
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.