Tying a knot in a button up is a fast way to transform it into a crop top. But if you don't tie the knot right, it can stick out and look lopsided, which isn't the look you're going for. Here's how to tie it so it lays flat and still looks good. The video above has a visual demonstration, but if you can't watch it, unbutton your shirt to the point where you want the crop top to end. Grab the two "tails" of cloth, making sure the side without buttons is on top, and tie your knot. The side without buttons should loop under the other tail and be pulled through the hole. Knot a second time to secure your shirt, again making sure the side without the buttons is on top. The knot should lay flat against your body.
How to Knot a Crop Top the Right Way [Refinery29 (YouTube)]