How do I use HomePod Minis JUST as AirPlay speakers?

We have had a pair of airplay speakers for a few months and I would like to find a way to just use them as airplay speakers for my phone/iPad.

I have no desire to use Siri, have it play songs or podcasts off the Internet or anything else. I just want to stream to it from my phone.

Currently, they will start playing songs at random and make it very difficult to stop playing them.

I have no interest in or need to have smart speakers.

Thanks