Wash and peel the potatoes. Cut the sweet potatoes into ¼” sticks. Then soak the sweet potato sticks in a bowl of water for at least 1 hour and up to overnight.
Once the sweet potatoes have been soaking for a least 1 hour, drain the water and remove any excess water off the potatoes with a towel. They don't have to be completely dry.
Preheat the oven to 450ºF and line a baking sheet with parchment paper.
Add the dried off sweet potatoes to a large plastic Ziploc or a reusable silicone bag (like a stasher bag). Add the oil, then the arrowroot powder and then the garlic powder. Shake and toss the ingredients around until the potatoes are completely covered. Add half of the salt and thoroughly mix in.
Place the potatoes on the baking sheet and spread them out evenly. They should all lay flat, side by side, not piled on top of one another. This is key for them to bake evenly. Bake them for 17 minutes.
After 17 minutes, remove them from the oven and flip them. They should start looking browned at this point. Put them back in the oven for another 5-10 minutes (mine were good after 7).
Remove them from the oven and let them cool for a few minutes. Add more salt if desired. Then serve with ketchup or your favourite dipping sauce.