Just use an Alexa ‘enabled’ group - see attached screenshot of an ‘example’ group.

If you give a voice instruction to play music etc. to a Echo/Sonos device held in the first/top section of the group, it will automatically group the speakers in the third/bottom section to playback the requested music.

Note too that the ‘playback options’ of the Alexa group ideally needs to be set to ‘Always’ so that there is then no need to include the group name in the voice instruction.

Note that any speakers without Alexa installed or built-in can be added to the second/middle section of the group and that will cause them to ‘duck’ the audio whenever the wake word and instruction is given to one of the Echo/Sonos devices that are enabling the group.

Hope that assists.