2. Take a pair of scissors. Any scissors will do, really. I think I used nail scissors.
3. Cut off the sleeves and neckline. Cut the sleeves below the shoulder seam but you can leave more or less sleeve on the shirt, as you like. No need to measure things or worry about straight lines. Nothing straight over here! The more crooked, the better, actually. In fact your cutting should be no less crooked than Snape’s nose.