Cut potatoes into finger-size sticks (about 1/2 inch by 3 inches).
Soak in cold water up to 1/2 hour, changing water once.
Drain and pat dry.
Place wok in ring stand.
Pour oil into wok to a depth of about 1 1/2 inches and heat to 375° on a deep-fat-frying thermometer.
Fry about 10 sticks at a time, turning as needed, to brown all sides (3 to 4 minutes).
Remove with a slotted spoon, drain on paper towels, and sprinkle with salt.