Grate the potato on the largest hole of a box grater.  Squeeze out as much moisture as you can from the grated potatoes. It's easiest to do this with a potato ricer, using it much like you would a garlic press, except you don't force the potatoes through the ricer. You just press out the moisture. I recommend doing this twice. If you don't have a ricer, use tea towels or paper towels to squeeze out as much moisture as you can from the grated potatoes.

Place a 10" cast iron skillet over medium high heat, add 2 tsp oil to the pan, and let preheat for 5 minutes.

When the oil in the pan heats up to the point of shimmering, but not smoking, scatter evenly with one-fourth the potatoes. The potatoes should not be too thick in any one place, no more than a quarter-inch thick. Sprinkle some salt on the potatoes. After a few minutes, lift up one edge of the potatoes and see how done they are. If they have fried to a golden brown they are ready to flip; it will likely take 3-5 minutes. Use a large spatula to flip the potatoes over all at once, or divide the large potato cake into halves or quarters and flip. Continue to cook until they are golden brown on the bottom.  Put this batch of potatoes on a plate to keep warm in the oven while you cook the rest of the potatoes, adding more fat to the pan first if necessary.  Serve immediately.