Chromecast Audio + Internet Radio

I would like to be able to play radio by pressing a single play button in action tiles. Ive seen people have a setup like this using Sonos. Since i already have great speakers ive purchased a Chromecast audio and connected it to my AV receiver. Right now i can click on a radiostation on my phone and stream it with chromecast. Then i start the music activity with logitech hub and voila there is music. So i would like to automate this so it can be done with 1 click.
But i have 2 problems. First of all i do not know how to add chromecast to ST and make it work with my receiver. Secondly i always have to press the cast button first. So i need my phone (in near future wall mounted tablet) to play all sounds through cast instead of using the phone speakers. For the radio source i want to put in the url of a direct radio stream or something like this. I dont not use Echo, sonos, Pandora, Deezer etc. Can anyone point me in the direction of how i can accomplish this? Preferably without adding extra devices like a raspberry, sonos or using a paid music service like deezer.

anyone knows?