Remove your oven racks. Set aside.
In a small bowl, mix a 1/2 cup of baking soda with 3 tablespoons of water. Adjust the ratio of both if needed, you want a spreadable paste.
Spread the paste all over the interior surfaces of your oven with your sponge, steering clear of the heating elements. Let the paste do its work overnight.
Also spread the paste all over the oven racks and leave overnight in the laundry sink.
In the morning take a damp sponge and wipe out as much of the dried baking soda paste as you can.
Put a little white vinegar in a spray bottle and spritz everywhere you still see baking soda residue in your oven. The vinegar will react with the baking soda and gently foam.
Take your damp cloth and wipe out the remaining foamy vinegar-baking-soda mixture. Repeat until all the baking soda residue is gone. Do the same with the oven racks.