Preheat the oven to 400°F (200°C)
Spread the fries in a single layer on a baking sheet
Lightly spray or brush with oil
Bake for 5 to 10 minutes
Flip halfway through
Remove when hot and crisp
Preheat the air fryer to 350°F (175°C)
Place the fries in the basket in a single layer
Heat for 3 to 5 minutes
Shake the basket halfway through
Remove when hot and crisp
Heat a skillet over medium-high heat
Add a small amount of oil
Add the fries in a single layer
Cook for 2 to 4 minutes, turning occasionally
Remove when hot and crisp
Avoid using the microwave if possible
Reheat only until warmed through
Serve immediately after reheating