With your shorter irons, concentrate on keeping your weight over your front leg on the backswing to eliminate any sway that leads to an inconsistent impact
For advanced players this drill works great to gain width in your swing and get you to a free release
The bottom of the clubhead should lie flat on the ground, if it lies on the heel the ball goes left and on the toe it goes right, which in turn will cause you to manipulate your swing, but the ball moves right and left depending on the club you are using so every club needs different amounts of manipulation