Starting by sitting at the catch, with the blade squared and buried. Take 10 strokes where you move only a few inches from the catch. Only your legs should move, with your body angle remaining constant and your arms straight. Then move to 10 strokes where you take half of the full leg drive, again keeping your body angle the same and arms straight. Then 10 strokes with a full leg drive. Then 10 strokes added the body swing, but still keeping the arms straight. And finally 10 full strokes.
Progression
The number of strokes at each position can be altered (perhaps moving it to 20), or each phase can be continued until the coach is satisfied that the technique is good.
Note
To ensure the boat is set during this drill, in larger boats, have rowers sit out with their blades flat on the water to help balance.