Preheat the oven to 425 degrees F. Line a sheet pan with parchment paper.
Scrub and peel the sweet potatoes. Cut them into evenly sized pieces; long, thin strips that are evenly wide.
Soak the potato pieces in a large bowl of cold water for 30 minutes (or more).
In a small bowl, whisk together the cornstarch, black pepper, garlic salt and smoked paprika. Set aside.
Drain the potatoes, turn onto a clean towel and pat dry. Rinse out the bowl and dry.
Return the potatoes to the bowl, add the cooking oil, and toss to coat evenly.
Sprinkle the cornstarch mixture over the fries and toss the fries in the bowl until they are evenly coated.
Carefully lay the coated fries out in a single layer on the prepared baking sheet. Bake for 15 minutes. Remove the pan from the oven and carefully turn the fries. Bake for 10 to 15 more minutes, until crispy and nicely browned.
Let the fries cool briefly in the pan on a rack. Sprinkle to taste with sea salt and serve.