A freezer would need vent holes drilled into it. Google--freezer incubator or something similar. There should be a lot of info out there. I just built one out of a wine cooler. Working great.
I found several threads where people had done it. Used their info so I did not have to experiment and "reinvent the wheel". I did have to move the fans around a little to get the temp right in all areas of the cooler.

How would a person get enough air flow in a big chest freezer? Use a small fan or what?
Scott