Cleaning ovens is potentially one of the most toxic things we do in our homes. Yet a mix of baking soda and soda ash can do the job for you. Mix together one cup each of soda ash and baking soda. Sprinkle the bottom of the oven to cover.
Spray with water until very damp, and keep moist by spraying every few hours. Let set overnight. In the morning scoop it all up along with the grime, and rinse.
If your oven is in a really bad way and has a lot of baked-on grime and grease, just use soda ash and add some white vinegar on hard-to-shift grime. Let it fizz for 10 minutes then scrub with steel wool. Keep applying both the soad ash and the vinegar and scrubbing until all the grime has gone.
You won’t get a headache from the fumes, or be polluting your house, but do wear rubber gloves as the washing soda can be quite tough on the hands.