If you're handy it's a bit of a coin flip. Some folks cut them into the removable panel covering the compressor end of the unit. That makes the AC wiring a piece of cake, just need to find a way to run the probe inside the cabinet.
I direct mounted a similar controller (MH1210) cut into the front edge of my chest freezer lid and ran the AC wires out the back edge, definitely more involved (though running the probe wire was easy). Otoh, all of my fridges have their controllers in project boxes sitting atop the cabinets, mostly because I didn't want to cut into any of their doors to mount the controllers. That's probably the most common way to go...
Cheers!