My Mac Mini (2011) was overheating so a designed a base to give it airflow. This base can be made in two prints on a 6"x6" bed. The surface area supporting the Mac does not change, and the center of mass is low so I do not believe it will have any tipping issues. I also designed little circles that fit in the indents on the bottom to remove sliding issues. It has been working so far for me.

Works with my 2011 Mini, but I think the base changed over time.

(Sorry for the crappy picture quality)