Vinegar and baking soda is what I use. Or bite the bullet and use EZ Off oven cleaner.
Hi Arlene, I would get a towel very damp and lay on the bottom of the oven and let sit for about a half hour to soften things up. Then take a plastic scraper or you could use an old plastic card, spatula etc. and scrape of what you can before you do the self cleaning.
Check out any consumer complaints on using self cleaning mode with your brand/serial number of oven. Some brands have reported "fried motherboards"...a horribly expensive replacement.
Hi Arlene: What I use is a paste of vinegar and cream of tartar (the dry stuff). Make a paste and put it on the gunk, even vertical surfaces. Let it sit for about 15 or 20 seconds and then scrape off with a plastic putty knife or one of those plastic scrubbies. You may have to do it a couple of times if the gunk is thick, but usually not. There is no smell and it is environmentally safe. Good luck.
Why not turn on the self cleaning and see how it does? If it doesn't get it all, then a second self cleaning. If there is still stuff left, try the wet towel method above. I say let the self cleaner clean! :)
My ovens that have had self cleaning do a really good job.