Slice your sweet potatoes into long, thin strips. It’s important that the fries are uniformly sized for even cooking.  Add the fries to a large bowl of cold water and soak for at least 30 minutes (or up to overnight).

Preheat the oven to 218°C / 425°F.  Line a large baking sheet with parchment paper, or spray with cooking spray.  Set aside.
Drain the fries, rinse out and dry your bowl well, then dry the fries with a clean kitchen towel.

Add the fries back to the clean bowl.  Then drizzle evenly with the olive oil, and toss until they are evenly coated.

In a separate small bowl, whisk together the cornstarch, garlic powder, smoked paprika and black pepper until combined.  Sprinkle the mixture evenly over the bowl of fries, then toss until the fries are evenly coated and the cornstarch has soaked into the oil.

Bake for 15 minutes.  Then remove pan from oven, and take the time to flip each fry with a spatula.  Rearrange so that the fries are evenly spaced and not overlapping again.  Then bake for 10-15 more minutes, or until the fries are crispy and have begun to brown a bit on the tips.

Transfer the baking sheet to a cooling rack, sprinkle with your desired amount of salt, then let the fries rest for 5 minutes.  Serve warm.