Place potatoes in a large bowl, and cover with cold water. Refrigerate for 8 hours. Drain, rinse, and pat dry.
Heat oil in a large pot over medium heat until it registers 310 degrees on a deep-fry thermometer. Line 2 baking sheets with paper towels. Carefully add potatoes to oil in small batches. Cook for 3 to 4 minutes, turning occasionally. (They will not color much.) Using a slotted spoon, transfer fries to paper towels to drain. Let cool.
Increase heat so oil reaches 350 degrees. Fry potatoes in small batches until golden brown, 3 to 4 minutes. Transfer fries to paper towels to drain. Season with salt, and serve immediately.
To make fries crisp on the outside with a fluffy interior, cook them at a lower oil temperature, let them cool, then fry at a higher temperature until golden brown.