The hitter needs to learn what it "feels like" to contact the ball correctly.
The way to practice contacting the ball is by not allowing "timing" to be an issue.
In the following drill, the coach tosses a consistent ball to the hitter.
It's important the toss is consistent to allow the hitter to hit without the need to worry about timing.
The focus here is on using the correct footwork, armswing, and contact for hitting.
The attacker begins the approach and the coach tosses the ball as they jump. The attacker approaches directly toward the net in front of the coach.
The coach tosses the ball only high enough for the attacker to take a swing in order to avoid problems with timing. The toss must be far enough off the net that keeps the attacker from hitting the net.