Full swing · Changes the swing

Flat lead wrist finish

Drawn setup
Illustration

Fix the finish and impact takes care of itself. With a 9-iron or PW, make a short swing to a three-quarter finish and stop. Check that the back of the lead hand is turned down and the wrist is straight in line with the forearm, not bent back. Optional: slide something thin and flat under the back of the glove so it lies along the forearm (the source uses a wooden spoon). Rehearse many times, then hit balls to the same finish and hold it 2 seconds.

Trains
Fat, Thin, Low point
Dose (suggestion)
10 rehearsals, then 2 sets of 10 balls
Count
Finishes with a flat lead wrist held 2 s, out of N
Stop signal
Stop: pain 3 out of 10 or more, pain spreading into an arm or leg, numbness, or more pain the next morning.
Source
MrShortGame Golf: The #1 Drill to Stop Flipping Your Golf Club at Impact