Preheat the oven to 400 degrees Fahrenheit.
In a large mixing bowl, add the almond milk, nutritional yeast, arrowroot starch, chopped garlic, onion powder, salt, pepper, and thyme, then whisk well.
Peel then thinly slice the potatoes (approximately 1/8 inch is perfect). You can slice them by hand or use a mandolin or food processor.
Use the oil to grease a large baking dish (I used a 9 x 13 inch rectangular dish, but any shape dish of a similar size will work).
Layer the potato slices evenly in the baking dish, then pour the almond milk mixture overtop.
Cover the baking dish with aluminum foil, then bake for 1 hour.
Remove the aluminium foil then continue to bake for an additional 15 minutes, uncovered.
Let rest for 5-10 minutes, then garnish with chopped fresh chives (optional) before serving.