Insulating The Truck Camper Fridge Compartment Update Good

Funny to compare that my Ford Model T has no water pump.
Thermal action is all needed to keep the engine from overheating.
I agree that having hot outside air circulating sides of the fridge makes no technical sense, but than building a seal on the back of the fridge would be big technical challenge.
If you made you side walls insulation snug with fridge side insulation, good for you, but what about bottom and the top?