To make the best, crispy smashed potatoes you will need something with a flat bottom to smash the potatoes. We find this easiest to do with the bottom of a cup or drinking glass, but it will also work with the back of a flat spatula, measuring cup, or even a potato masher. If you are using a potato masher, just be sure to press down on the potatoes gently or place a piece of parchment paper between the potato and the potato masher. This will help keep the top surface of the potato flat and smooth.