I'm not a fan of the look of those shirts, but from what I can tell, they basically start at the seam at the top of the shoulder and cut a large hole down the side of the shirt. Basically you're cutting off the sleeve and then some. I'm not sure how to explain it well but I've been told that the initial look was to just cut off the sleeves and the shirts eventually look like that, but I don't believe it. They made them that way, I'm betting. Also, even after you have the side holes if your shirt still looks "smock-ish" wash and dry it and if you still don't like the look of it, you can start cutting in on the seam on the top of the shoulder. Be careful not to completely unravel the entire seam or the shirt will fall apart but basically you could start to "tailor" it to look like you want. I know lots of people that cut V's into the neck of their round collar shirts to provide increased range of motion.