Choose a pot large enough to hold the potatoes without crowding (4 to 5 quarts) and fill it with cold water. Drop the potato sticks into the water to rinse off the starch. You can immediately remove the potatoes from the water and proceed to the next step. Or if you want to prep the potato sticks in advance and roast them later in the day, you can leave them in the water. If you plan to wait more than 2 hours before roasting the fries, however, put the pot in the refrigerator.

Drain the potatoes, rinse well, and return them to the pot with enough cold water to cover by 1-1/2 inches. Add 1 teaspoon kosher salt. Partially cover the pot, and bring the water to a boil over high heat. As soon as the water boils, reduce the heat to a calm boil and boil for 3 minutes. Gently drain the potatoes in a large colander and then spread them on paper towels to dry. (The potatoes can sit for up to an hour before roasting.)

When you're ready to roast the fries, put a baking sheet on the middle oven rack and heat the oven to 450 degrees F. Put the potatoes in a large bowl, add the olive oil, and toss to coat the potatoes, being careful not to break the sticks. Remove the hot baking sheet from the oven and arrange the potatoes on the sheet, leaving at least 1/2 inch between each. Roast, turning the fries over and rotating the baking sheet once after 15 minutes and then again every 6 to 8 minutes, until the fries are nicely browned and crisp, a total of about 30 minutes Sprinkle with fleur de sel or lemon-fennel salt, toss gently, and serve immediately.

Lemon-Fennel Salt: Toast the fennel, coriander, and peppercorns in a small, dry skillet over medium heat until fragrant, about 2 minutes. Pour into a mortar or spice grinder and grind to a fine powder. In a small dish, combine the lemon zest and salt with the spices.

Make Ahead Tip: This salt will keep in the refrigerator for up to three days.