Are there not detailed instructions on the Sonance website, if not in the box?

I’d think a pole mount, set in a concrete base or if you want a redwood 4x4 post mount that would be prettier would be your best simple options. If you want to go fancy a sun/weather shielded mounting box could be used.

https://www.sonos.com/pdfs/productguides/en-us/sonos_outdoor_by_sonance.pdf

I just use 4x4 posts that are treated and rated for direct ground contact.  No need for a concrete base really.  The post puts the speaker about 4 feet off the ground.  I would not try and use these speakers very close to ground level as they are not designed for that.

The 4x4 post shouldn’t need a concrete base except in very weak soils, the pole option (particularly small diameter ones) doesn’t have the same resistance to movement so it needs concrete to lock it in place even in medium soil.

Agreed.  I was thinking similar, but didn’t type that for some reason.  Not sure what type of soil I have, but have 4 posts  in one area that have not ever moved really.  2 more I did recently have moved.  Not sure if it was different soil, or I didn’t bury the post deep enough.

Thanks, everyone - much appreciated!