Cut the potatoes.
Scrub the potatoes and cut them into fries about ¼–⅜ inch thick. You can leave the skins on.
Soak them.
Put the cut potatoes in a bowl of cold water for 20–30 minutes. This removes some surface starch and helps them get crispier.
Dry REALLY well.
Drain the potatoes and thoroughly dry them with clean kitchen towels or paper towels. The drier they are, the crispier they’ll get.
Preheat the oven to 425°F.
For an extra-crispy bottom, put your baking sheet in the oven while it preheats.
Season.
Toss the dry potatoes with the cornstarch first, coating them very lightly. Then add the olive oil, salt, garlic powder, onion powder, paprika, and pepper.
Spread them out.
Arrange the fries in a single layer on the baking sheet. Don’t pile them on top of one another. Two baking sheets are better than overcrowding one.
Bake for about 20 minutes, then flip the fries.
Return them to the oven for another 15–25 minutes, until they’re deeply golden and crispy.
Salt immediately after removing them from the oven.