Cut each potato into an even rectangular shape by cutting off the bottom, top, and sides, then cut into 1/2-inch cubes. Put in a medium, heavy saucepan and add enough water to cover. Bring to a boil and cook until the potatoes are slightly tender, about 10 minutes.
Remove from the heat and drain on paper towels.
Heat the oil in a large, deep, heavy pot or an electric deep fryer to 360 degrees F. Add the potatoes and fry, turning to brown evenly, for 3 to 4 minutes.
Remove and drain on paper towels. Season with salt, and serve hot.