Preheat oven to 350 degrees.
Wash and scrub the sweet potatoes. Lay sweet potatoes on their side and thinly slice and slice into 1/2 inch rounds. You may slice them thicker, just make sure to add more baking time.
Melt 2 tablespoons of butter in a glass dish with the chopped garlic and fresh thyme.
In a large mixing bowl, add the sliced sweet potatoes with the melted butter mixture and kosher salt. Use your hands to make sure the sweet potatoes are mixed up and not stuck together.
In a small oval baking dish or even a pie dish, use the extra butter to coat the dish. Layer in the sweet potatoes on their sides.
Cover the dish with foil and bake in the oven for 30 minutes. Remove the sweet potatoes from the oven, turn up the heat to 425 degree. When the oven is ready, remove the foil and place the sweet potatoes back into the oven for another 20 minutes, until tender.