The primary cause of mis-struck iron shots comes from golfers not being aware of where the bottom of the swing arc needs to be. Many believe the bottom of the swing is the ball itself, which causes an array of fat and thin strikes.
The bottom of the arc needs to be after the ball to create that ball then turf contact. A great way to shift your arc forward is feel your pelvis shift forward into impact. This practice drill from Approach Zone Instructor Adrian Fryer uses your golf bag to encourage you to do this on every swing, hitting those crushing iron shots with a piercing trajectory.