Preheat the oven to 350 degrees F. Set a cooling rack over each of 2 baking sheets.
Peel the potatoes, leaving a patch of the skin at both ends. Cut each potato lengthwise into very thin (1/8- to 1/4-inch) slicesthe thinner they are, the crispier the end product will be. Cut those slices into strips that are just as thin.
In a large bowl, drizzle the fries very lightly with EVOOa couple of turns of the bowl should do the trick. Season with salt and pepper. Arrange the fries on the racks in a single layer without crowding either rack. Roast 30 minutes.
Remove the fries and increase the oven temperature to 425 degrees F. Toss the fries in a large bowl with one of the optional flavoring (if using). Return the fries to the oven and bake until very crispy and brown, 15 to 20 minutes.