Take a mid-iron and then adopt a square address position in which your shoulders, hips and feet are all parallel to your target line (see photos 1-4 in PDF below). Now rotate the Alignment Bar so your feet are at 30 degrees, so that you right foot is slightly behind you and practice some swings from that position. This closed stance will help you to clear your right side on the backswing and get your back facing the target. When you swing back down, you should feel as if you are swinging along the line of the Foot Alignment Bar in order to produce an in-to-out swing path (see PDF below), this coupled with the correct forearm rotation will help you close the clubface and produce a nice draw shot, instead of a slice.
Note: You should practice this drill in slow motion to start with and then steadily increase your speed until you are swinging normally. Once competent at 30 degrees, repeat the process with the Alignment Bar at 20 degrees and then 10 degrees before returning it to its original position aiming directly at the target. By this time the in-to-out swing path and forearm rotation should be ingrained into your mind and you should be hitting much straighter shots.