Preheat the oven to 230C/Gas 8.
1) Cut the potatoes lengthwise into 1/2-cm thick matchsticks, and toss with the oil and 1/2 teaspoon salt.
2) Spray a baking tray with cooking spray. Arrange the potatoes in a single layer on the baking tray and bake until the chips are tender and crisp, about 30 minutes.
3) Season with additional salt, to taste. Serve immediately.