I found your question interesting. I've flown by the seat of my pants in this regard in the past and I wondered if there are rules. I did a bit of research, I found this at The Kitchn:
https://www.thekitchn.co...roles-tips-for-re-137981
That llinks to this website which has lots more detail, and I include it here, because it's easy to miss the link:
https://www.joyofbaking.com/PanSizes.html
The short version is that casseroles aren't too sensitive and if you fill the pan to the same depth as it would have been in the larger pan you don't really need to adjust time and temperature.
bittrette;23649 wrote:My stove is on the fritz. It goes on and off without warning, usually at the most inopportune times,
If the oven is going on without being turned on, that is a real safety hazzard and you should unplug it immediately. I worked in a small bakery during high school and commercial ovens are never turned off. Due to their size, they take too long to come up to preheat. They are merely turned down. Well, the thermostat on the oven failed and the oven stayed on 24/7 over a long weekend I think it was. Anyway, the oven got hot enough it caused the floor to smolder and weaken. By the time it was discovered, the floor was failing and the oven partially collapsed into the basement. Luckily the gas line wasn't severed or the entire block would have gone up in the explosion.
If it is a gas oven and it is simply failing to stay on, it is either the thermocouple or the thermostat, both of which are relatively affoardable repairs, if you are comfortable having a repair person in your home right now.