Peel the sweet potatoes and slice into 1/2-inch rounds. Coat a 9×13-inch ceramic baking dish with cooking spray (avoid metal pans; they can add a slight metallic flavor). Add the potato slices, sprinkle with salt, and toss to coat. Preheat the oven to 375°F. In a medium pot over medium heat, add the butter, brown sugar, maple syrup, cinnamon, nutmeg, ginger, and cloves. Cook, whisking occasionally, until the butter melts. Stop stirring and bring to a gentle boil. Boil for 2 minutes without stirring.