When I do that, like with baked beans or dressing, I usually have the oven on cooking something else, and it does a good job of keeping things warm. So you could just set your oven at about 200, and your dish will stay warm without overcooking.
I have also set finished dishes inside the microwave, which is well insulated. If it's for very long, I give it a little zap now and then.
Coolers also keep things hot as well as cold.
Hope I helped!
Now, if you ever need any help with ways to keep food cold when you are totally out of refrigerator space and coolers, let me know.
We get by with a little help from our friends