If you have two of the same model Google Assistant speakers, you can create a stereo speaker system.

How to create a stereo pair...

1. Open the Google Home app
2. Find the speaker you want to setup in stereo pair
3. Find the speaker/room
4. Tap on Settings
5. Go to Sound Settings
6. Find the Speaker pair
7. You are now entering the setup page Tap
8. Find your speaker under the Pair with list and tap.
9. Move the speaker to be Left or Right side and press
   1. You can tap on Play sound to identify which speaker it is.
10. Find a name for your Stereo pair
11. It takes a minute to complete the setup.
12. When the configuration is done it will say Ready
13. Press Done

You have now completed the setup and created a Stereo pair sound experience.

NOTE 1:  This is only possible with two of the same speakers.  If they are not identical (Example: Citation 100 & Citation One), setting up a stereo pair will not be an option.

NOTE 2: It is only possible to use Chromecast and Bluetooth in stereo, Airplay will be mono (and should be grouped in iOS Airplay menu.