Wash and dry the skins of the sweet potatoes. If necessary, cut off the ends on each side to have them clean. Cut the potatoes vertically into fries about half an inch thick.
Transfer to a bowl and drizzle with olive oil to lightly coat the pieces. Sprinkle with sea salt and cinnamon or cumin and mix. Place the fries on top of a metal cooling rack over a cookie sheet and place into a preheated oven.
Cook for 40-60 minutes, turning halfway through.
For a different taste, replace cinnamon with Cajun seasoning or garlic powder, in addition to the sea salt.