No Problem!
You just need to buy a trailer that is not too long for the spot.
The trailer DOES NOT need to be level for storage, it only needs to be level for running the propane refrigerator, so you will not be able to pre-cool the fridge when it is on this angle. I guess you could put it in the street for a day to pre-run the fridge?
Of course you will need to block the tires so it will not roll down.
Having the trailer on a slope will be good for getting rid of rain water and preventing it from pooling on the roof.
If the rear of the trailer will drag then look into getting some little steel wheels made for dragging rear ends - as long as the angle is only slight the wheels will work (like if the trailer only needs to lift an inch or two to make it, where the tires still are on the ground, but just the suspension is lifted a little).
People drag the rear of trailers all the time, you can see evidence in those gas station driveways that have huge bumps.