I live in a small house and I found that the space taken up by my Echo Dots was a nuisance - mainly because they have to be a reasonable distance from walls, etc. In the end I solved this by creating this simple wall bracket which holds the Dot in place on the wall or any other vertical surface. As you can see it also acts as a convenient cable tidy!
The design is simple and is a close fit for an original Echo Dot (I can't comment any later products). The close fit means that the device pushes in and the USB cable then secures the device in the bracket without having to use any adhesive. You can see from the photo that mine isn't even screwed to the wall, I simply used 3M Command Strips and they're strong enough to hold it in place.
Note that sound quality is compromised! Even with the air gaps that are included in the design, the audio quality becomes quite tinny, losing much of the Dots bass. I use a Bluetoth speaker with my Dot so this was no issue for me but be aware of this if you use your Dot to play music, etc.
This object was made in Tinkercad. https://www.tinkercad.com/things/gh7TfKORj2C