This is a simple solution to mount your Sonos One (and One SL) to a wall outlet. The clean design combines with the wall plate (linked below) will support the speaker and hide the cable and will allow the use of the outlet below.
Inspired by other mounts for HomePod mini (linked below), I wanted something that would work with my Sonos speaker but needed to be redesigned for the additional weight and size.
Use this faceplate for US duplexes, remixed from @CharlieEssers remix of a wall plate. This one has been strengthened for the additional weight of the Sonos speaker:
https://www.printables.com/model/1195179-sonos-one-wall-outlet-mount-for-us-duplex-receptac
Use this faceplate model for GFCI/combo plates initially used in a HomePod shelf design:
https://www.printables.com/model/93072-homepod-mini-wall-outlet-shelf/files
The author marked this model as their own original creation.