Prep the potatoes: Toss the cubed potatoes with the olive oil until evenly coated. In a separate small bowl, whisk together the cornstarch, garlic powder, smoked paprika, and salt. Sprinkle this mixture over the oiled potatoes and toss again to ensure every cube is lightly dusted. The cornstarch helps draw out moisture for crispiness.
Heat the oven: Preheat your oven to 450°F (230°C). Place a large, heavy-duty baking sheet in the oven during preheating if you want extra crispy bottoms, though lining a regular sheet with parchment paper works fine too.
Roast: Arrange the potatoes on the hot or prepared baking sheet in a single layer. Ensure there is space between each cube; do not stack them. Roast for 15 minutes.
Flip and finish: Remove the pan from the oven. Use a spatula to flip each piece over. You should see golden-brown edges forming. Sprinkle with black pepper and a pinch more salt if desired. Return to the oven for another 5-10 minutes until the potatoes are tender inside and deeply browned outside.
Serve: Check doneness by piercing a cube with a fork; it should slide in easily. Serve immediately while hot.
