Lightly grease a casserole dish large enough to fit all the ingredients. Then add the sliced sweet potatoes and pour over the sauce (melt the butter and combine it with the orange juice, vanilla, and spices). Cover the bake dish with aluminum foil and bake at 400ºF/200ºF for about 40-50 minutes. Stir halfway, removing the foil to allow the sauce in the baked candied yams to thicken. If it needs some help, add a spoonful of cornstarch slurry to the old-fashioned candied sweet potatoes. Bake until the brown sugar glaze has thickened.