The cooking time for lotus root slices can be affected by a number of factors, including the thickness of the slices and personal flavor preferences. Lotus root slices need to be cooked for about 5 to 10 minutes to cook through. The best way to observe the lotus root slices frequently while cooking is to gently poke the slices with chopsticks; remove them when they can be inserted easily and the texture of the slices is soft and cooked.