Players split into a team of servers and another of passers. The serving team tries to tally 10 aces before the passers get 40 good passes.
The goal is not passing or serving accuracy. Its real purpose is to reduce errors, either from missing serves or getting aced. Three over-passed balls gets recorded as an ace for the serving team. Three missed serves counts as a good pass for the passing team. An imperfect pass is simply a wash.
To use this drill in your practice gym, check out this video for additional pointers on setup and implementation.