The Ubiquiti UniFi Security Gateway (USG) Is a great router, but they run very warm if placed on a flat surface or when stacked with other equipment. Here are three sets of feet for spacing them out in Horizontal or Vertical orientations with allowance for airflow.
I've included the original Sketchup files, plus the smoothed versions, in case you want to fiddle with them. I used Fredo Round Corner for smoothing the edges.
You'll want to print them in an orientation that doesn't require supports.