While the boat is stationary, start from the finish with the blades in the water. You can do this drill by pairs, fours, sixes, etc. and inside hand, outside hand, both hands on the square, feather, et al. 

Sitting at the finish, extract the blade and keep good seperation out of bow. Arms, body, then slide. You want to keep good posture and be patient to place the blade into the water.

Make sure that placement is direct and not disruptive to the boat. Hold the body position at entry to help the athlete feel comfortable in this position.

Add in pairs as the boat remains stable.