Lay the old towel in the bottom of the bathtub to prevent scratching.
Place the oven racks on top of the towel.
Put the plug in the drain and fill the bath with water, gradually adding the laundry detergent as the bath fills.
Leave the oven racks to soak overnight or for 6-10 hours.
Use a soft sponge to gently lift any remaining grease, then use a toothbrush for hard-to-reach places. Rinse thoroughly in cold water and dry.
