Peel the potatoes, if desired. Use a large-holed cheese grater or food processor to shred the potatoes. Place the potatoes in a colander and rinse well, or until the water runs clear. Let the potatoes drain.
Squeeze the potatoes of their excess water by pressing against the side of the colander or squeezing in your fist. Or, place the potatoes in a clean, lint-free dish towel, roll them up, then press to remove excess moisture.
Heat a large cast iron or non-stick skillet over medium heat***. Once hot, add a tablespoon of cooking oil. Tilt the skillet to spread the oil over the surface. Add about 1/3 of the shredded potatoes or enough to cover the surface of the skillet in a solid, yet thin layer (1/2 inch thick or so). Let the potatoes fry, without disturbing, until deeply golden brown on the bottom (3-5 minutes). Season lightly with seasoning salt.
Flip the potatoes, and drizzle with additional oil if needed. Let the potatoes cook on the second side without disturbing until golden brown and crispy again. Season lightly on the second side.
If needed, flip and cook one more time to achieve the ratio of brown to white that you like. Repeat the process until all of the potatoes are cooked. Serve hot.
*I use Russet potatoes because they crisp up great in the skillet due to their texture and composition. You can certainly try another type of potato, but just keep in mind waxier varieties might not crisp up the same.**You must use an oil with a high smoke point, like canola, corn, peanut, or sunflower oil. Butter obviously gives amazing flavor, but the butter solids tend to burn, so you'll want to use clarified butter or ghee instead. I didn't have the patience to clarify any butter, so I just used canola oil. ***I always use my 10" cast iron skillet because it offers non-stick protection while giving really even heat and a nice surface for crisping. While stainless steel is also great for crisping, starchy foods (like potatoes) tend to stick a lot more on stainless, so it can be tricky. If you're not well practiced with keeping food from sticking on stainless steel, I'd suggest either cast iron or a non-stick skillet.