Choose potatoes that are 4 to 6 inches in length to ensure well-proportioned fries. Trimming thin slices from the ends of the potatoes in step 2 ensures that each fry has two flat surfaces for even browning. This recipe’s success is dependent on a heavy-duty rimmed baking sheet that will not warp in the heat of the oven. Spraying the sheet with vegetable oil spray will help the oil spread evenly and prevent sticking. The rate at which the potatoes brown is dependent on your baking sheet and oven. After removing the aluminum foil from the baking sheet in step 5, monitor the color of the potatoes carefully to prevent scorching.

1. Adjust oven rack to lowest position and heat oven to 425 degrees. Generously spray rimmed baking sheet with vegetable oil spray. Pour oil into prepared sheet and tilt until surface is evenly coated with oil.

2. Halve potatoes lengthwise and turn halves cut sides down on cutting board. Trim thin slice from both long sides of each potato half; discard trimmings. Slice potatoes lengthwise into 1/3- to ½-inch-thick planks.

3. Combine 1/3 cup water and cornstarch in large bowl, making sure no lumps of cornstarch remain on bottom of bowl. Microwave, stirring every 20 seconds, until mixture begins to thicken, 1 to 2 minutes. Remove from microwave and continue to stir until mixture thickens to pudding-like consistency. (If necessary, add up to 1 tablespoon water to achieve correct consistency.)

4. Transfer potatoes to bowl with cornstarch mixture and toss until each plank is evenly coated. Arrange planks on prepared sheet, leaving small gaps between planks. (Some cornstarch mixture will remain in bowl.) Cover sheet tightly with lightly greased aluminum foil and bake for 12 minutes.

5. Remove foil from sheet and bake until bottom of each fry is golden brown, 7 to 15 minutes. Remove sheet from oven and, using thin metal spatula, carefully flip each fry. Return sheet to oven and continue to bake until second sides are golden brown, 7 to 15 minutes longer. Sprinkle fries with ½ teaspoon salt. Using spatula, carefully toss fries to distribute salt. Transfer to paper towel–lined plate and season with salt to taste. Serve.