I used PETG but should work with anything rigid. I used auto support in Prusa Slicer to make sure the tabs printed OK, it broke off cleanly. Cable can be routed through side hole if desired but made a nice snug fit even without that.
CAD File available: https://scalora.net/content/cad/Echo-Dot-Mount-v5.f3d
The author marked this model as their own original creation.