permanently grouping sonos 1 and era 300

Hi. I have just purchased an era 300 to add to an existing Sonos 1 in our lounge. How can I get these so that they are permanently grouped and always come on in sync, either on the alarm or when I ask Alexa. It worked fine when I had two Sonos 1s paired but recognise I can’t do a stereo pair with the different products but i do still want to group them so they play together.