Fill a large bowl halfway with cold water. Set aside. Using a sharp knife or mandoline, slice the potatoes into thin fries (about 1/3"-1/2" thick). Transfer the cut potatoes to the cold water. Swish the potatoes in the water with you hand and drain the water from the potatoes. Refill the bowl with cold water and rinse again. Use paper towels to pat dry the potatoes.
Add the oil to a medium dutch oven. Put the potatoes into the cold oil. Place the oven on the stove and turn the heat to medium-medium high. The oil will bubble briskly once it comes to temperature. Cook the potatoes for 25-30 minutes until crisp outside and tender inside, stirring occasionally.
Meanwhile, line a baking sheet with paper towels and set aside.
Use a spider or slotted spoon to scoop out the fries and transfer them to the baking sheet. Immediately sprinkle the fries with salt. Serve.