I use an old round griddle on the bottom of my oven, (dual purpose, I can also make pancakes on the stove top or campfire when I want to), and a double layer of foil.
You might experiment cooking on your upper and lower rack setting too.
I also use my dutch oven for many things, I have my grandmothers 4" high cast iron dutchy with handle, some call it a cake fry pan, for general baking, that way I can sear my roast, add onions, etc. and then just throw it in the oven.
I have never had a leaning problem, but my husband is fanatical about being level.
I also use an oven thermometer, wouldn't live without it! RV ovens are tempermental! But I have got to the point where I have cooked and entire Thanksgiving dinner in one, (in stages, of course!).