NEW VERSION 4/22/2019
This mount is a remix by Din_D, which is a remix by mgx. I used their concept as inspiration, but changed up the design a bit.
The mount requires no hardware and no supports to print. I measured the Amazon Echo Dot and fount it to have a tapered body, just like mgx, which means that if your printer scaling/extrusion is off a small percentage it should work just fine, and you can wedge the Dot firmly in place. The portion that fits around the outlet allows you to slide the mount deeper or shallower, so that you can get the Dot as close to the wall as possible, to relieve the loading on the outlet itself.
I made it a vertical mount only, because having the dot stick out horizontally seems like would add some unnecessary cantilevered load to the outlet, which may or may not be safe.
I also slimmed their design down a bit and cleaned the sharp edges up with some fillets for aesthetics.