The Perfect Grip
The key in order to attain a flat left wrist at impact, is the way you hold the club.
What is a perfect grip? Answer: the one that gets the clubface to be square on separation of the ball from the clubface, and ensures you have a flat left wrist at impact.
Look at your ball flight. In most cases the club golfer swings the ball from left to right - a sliced shot.
Turning your hands a little to the right would help square the face. You would then start hitting straight left.
If this happens it is because you have aimed yourself to the left of parallel to the target line to allow for your slice.
So next, check your aim, and ensure your feet, knees, hips and shoulders are parallel to the target line.
Fellow of the Professional Golfers' Association