Re-arranging your entire setup when your ball has landed in a divot is one thing, but to alter your swing when a backswing is nigh impossible is another one. Altering your stance and your swing plain is really difficult, so any advice here is solid gold.
The Plan of Action
The whole idea of this shot is to put the obstruction clearly out of the picture. This is done by taking the swing so far inside of your swing plain, which in theory will erase the need for a backswing.
How to setup for this shot
Starting off with your usual stance and ball setup, imagine hitting the ball without and obstruction behind you. What you do from this position is, rotate your body clockwise so that your toe line is in line with your target. Also, your chest should be facing the obstruction here. You should aim to make your stance as closed as it possibly can, which it is if your back is perpendicular to the target line. To hit a firm shot here, you will need to have the ball to the left of your front foot.
These type of shots carry a great deal of hook to them, so to counter-act this you will need to lighten up on your grip of the club. This will allow your wrists more freedom when hitting through the ball, whereas as if the grip was a little too tight, the clubface would close and the ball would hook way beyond what we require it too.
One key thing to remember throughout this type of shot is to envisage your swing plane to be along your toe line, so that it remains well inside your swing plane. When you are beginning your backswing you should feel as though your hands are going into your right back pocket. When you begin your downswing you should feel as though your hands and club are going to smash into the side of your right hip. If you can imagine both of these throughout your swing you will have the technique down to tee (pardon the pun).
Keeping your hand firmly still throughout this movement is another key aspect. Keeping your head still throughout your swing will prevent any sliding, (forward or back) which is something that is very common in this strange type of swing. To keep as much control as possible over your shot, you should aim to keep your swing to roughly 3/4's of what your usual full swing is on any other iron shot. Because of the increased hook involved with this shot, it's important to take extra precautions and plan in advance the increased distance on the shot.
The last touch for shorter backswing
The biggest problem with many golfers and this shot is the desire to hit towards the target. This is a no no. Doing so will result in hitting the obstruction you are trying to play around. Just make sure you hit through your toe line, and then the baby should hook.
Another word of warning for this shot: Try not to increase the hook of this shot with the wrists, fingers, hips, or any other part of the body. Doing so will only result in a duffed shot. The setup for your swing and the swing plane you swing through will do the hooking for you.
Hopefully, if you play well and luck is on your side, you will never have to play a shot like this, but if you do, this information will serve you well. Just in case this situation does arise, it's always too good to give it a little practice before hand. When you're at the practice range next time round, use your bag as the obstruction and practice a few shots using the method you've learned here.