Use a cloth or knife to quickly remove any loose debris from the bottom of the oven. Don't worry about trying to scrape off anything that gets stuck, it will come off more easily later.

Thoroughly coat the inside of the oven with the cleaner of your choice. Make sure it covers the walls, floors, ceilings and doors (even glass) that really get into the nooks and crannies.

  If you have a lot of burnt on the bottom of your oven, give it a thick coat of cleaner or bicarbonate paste. That way, it will have enough volume to penetrate the dirt, allowing you to remove it faster and easier.

  After applying the cleaner to every surface inside, close the door and let it soak in.

  Oven cleaners specify their wait time in their instructions, usually around 30 minutes. If you use sodium bicarbonate, this paste will de-grease after about 30 minutes to an hour in most ovens. However, you can also leave it for up to 12 hours to easily clean even the worst ovens.