Preheat your oven to 220°C (430°F) and line a baking sheet with parchment paper or a silicone mat.
Wash and peel the sweet potatoes, then slice them into thin matchstick-sized strips about ¼ inch thick using a sharp knife or mandoline for uniformity.
Place the sliced sweet potatoes in a large mixing bowl, then drizzle with the olive oil, tossing gently to coat each piece evenly. The fries should glisten with oil and feel slightly slick to the touch.
Add the sea salt, black pepper, smoked paprika (if using), and the cornstarch or arrowroot powder to the bowl. Toss again until all the slices are well coated; this helps create a crispy exterior.
Arrange the seasoned slices in a single layer on the prepared baking sheet, leaving space between each piece to ensure proper crisping and prevent sticking.
Bake for 15 minutes, then carefully flip each fry with tongs or a spatula to promote even browning. Return to the oven and bake for an additional 10–12 minutes, or until edges are deep golden and crispy, with some caramelized spots.
Watch closely during the last few minutes—once the edges are crisp and browned, remove the fries from the oven and let them rest for 2 minutes on the baking sheet. They will firm up slightly as they cool.
Serve the hot fries immediately, sprinkled with a little more sea salt or a squeeze of lemon if desired, to enjoy their full crispy and caramelized flavor.
