Peel sweet potatoes, then cut into thin fry-shaped slices.
Fill a bowl with cold water and add sweet potato slices to the bowl. Let soak for an hour or overnight.
Drain water from bowl and rinse sweet potatoes with cold water. Place on dish towel and pat dry.
Measure out corn starch and place into a zip-top plastic bag. Add sliced sweet potatoes and shake until potatoes are evenly coated with corn starch. (You may have to do this in several batches, depending on the size of your sweet potatoes. Thus, add cornstarch as needed.)
Heat a large stainless (or cast iron) skillet on med-high (closer to high) heat, adding coconut oil to the skillet. Let oil heat up until you start to see smoke coming from skillet. Then carefully place sweet potatoes into the skillet, watching that the hot oil doesn’t splash up and burn you. (Add more oil as needed.)
Stir fries until most are brown and crispy. Finish off in the oven (pan and all, if it’s a metal pan) for about 10 minutes, stirring once.
Remove from oven, sprinkle seasoning of your choice over the fries and enjoy immediately.