Set the oven to 450°F (230°C). Place a large sheet pan inside to preheat for 10 minutes. Hot pan = instant sizzle = crispy fries.
Wash potatoes and peel if you want classic smooth fries. Leaving the skin on adds texture and fiber. Your call.
Slice into 1/4- to 1/3-inch sticks. Keep them uniform so they cook at the same rate. Wobbly fries = wobbly results.
Submerge the cut fries in cold water for 20–30 minutes. This pulls off excess surface starch, helping them crisp instead of steam.
Drain and spread on a clean towel. Pat very dry. Moisture is the enemy of crunch.
In a large bowl, toss fries with cornstarch until lightly dusted. Then add oil and toss to coat evenly. No powdery spots; no greasy puddles.
Add salt, pepper, garlic powder, smoked paprika, and onion powder. Toss again so every fry gets love.
Carefully remove the hot sheet pan. Line with parchment or lightly oil it. Spread fries in a single layer with space between. Overcrowding equals steaming. Don't do it.
Bake 15 minutes. Flip with a spatula, rotate the pan, and bake another 12–18 minutes until golden and crisp at the edges.
While hot, hit with a pinch more salt. Add parsley, parmesan, or vinegar if you're feeling fancy. Serve immediately with your favorite dip.