This is by far the easiest oven door cleaner that I have used to date: super easy, no toxic fumes, just add hot water, borax and elbow grease!
The photo below shows the section of the door that I have cleaned.
First turn your oven onto 180 and put an oven proof dish in filled with hot water, leave for 20 or 30 minutes to let the steam/moisture soften any gunk on the oven door.
Get your borax and sprinkle onto a cloth, add a little warm water and start to wipe in a circular motion, this will bring up your oven door really well. Keep going until you’ve removed any grease and grime.
To finish off wipe over with a clean sponge and water. You can also clean the glass with oven cleaner.