You plug the fridge into the controller and put the temperature probe in the fridge. The controller cycles the power to the fridge as needed. Since the fridge 'wants' to be colder, it always runs when the controller gives it power.
Cost/availability depends on your location.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk