The cooking time of lotus root slices is affected by the thickness of the slices, the cooking method and the taste requirements. Thin slices of lotus root should be cooked in boiling water over medium heat for about 5 minutes to achieve crispness and tenderness, while thicker slices of lotus root need to be extended to about 10 to 15 minutes to ensure full doneness. For a softer texture or for use in soups, extend the time to 20 minutes.