Many golfers can not get into a proper set up position and posture because their hamstrings are too tight to allow the straightening of the back, so before you tee off or practice work on stretching out your hamstrings so that you can work the golf swing properly around a straight back
Method teaching is a one swing fits all philosophy that teaches all players identical swings based on the assumption that this method is the perfect swing
With a shaft placed in the ground just outside and in front of your ball practice your follow through making sure that you go underneath and release below the shaft