How to we keep the crisp part of French Fries for longer time

I take a piece of aluminum foil, crumple it up then smooth it out somewhat still leaving slight concave and convex angles for the fries to crisp evenly without the need of flipping halfway through baking.

There are a couple tricks I've learned from Cook's Illustrated about making oven fries:

1. Soak your cut potatoes in warm water to rinse off excess surface starch. Drain them and dry them very well (I use a salad spinner and paper towels).

2. Use a heavy duty sheet pan on the bottom rack of a hot oven to focus the heat on crisping the bottoms of the potatoes.

3. Oil your sheet pan well, and sprinkle salt on it. This will act kind of like ball bearings under the potatoes to prevent them from sticking too hard.

4. For the first 5-10 minutes, tightly wrap the sheet pan (with the potatoes) with aluminum foil. This will essentially steam the potatoes and help get a really nice creamy interior. After that, remove the foil and flip the potatoes halfway through. Make sure you use a thin metal spatula when you flip them.

These techniques work well for potatoes in general, and really do turn out some fantastic spuds.