[gshodg]

, just create the OpenELEC install media (you can run the EZ Setup Script from Ubuntu), boot it, and install OpenELEC - that's it.

I'm not sure what I need to do to create the OpenELEC install media. I followed your wiki to great success for the initial install, but now I'm stumped, could you help me with the steps I need to use your script to reinstall OpenELEC please?

...
the reason I ended up with Ubuntu installed was following these steps, the BOLD bit (I guess I misunderstood them). I now don't have the Ubuntu boot USB, as I tried to use Google utility to make a bootable USB to get back to Chrome OS. So now I'm back at the SeaBIOS black screen.

If you have standalone setup, it is necessary to restore the stock firmware before performing a factory reset to reload ChromeOS.
In order to do this, you will need to download/run the ChromeOS device Firmware Utility script and select the appropriate option from the menu. The script will give you the option to restore from either a backup file from USB (which you created before originally flashing the custom coreboot firmware) or from a generic copy extracted from Google's recovery image. Like the Kodi EZ Setup Script, this script must be run from a Linux terminal with a full bash shell; OpenELEC users will need to boot a Linux Live USB (Ubuntu 14.04.2 64-bit works fine) from which to run the script. Just download the ISO of and write it to USB using Win32DiskImager (from Windows) or dd (Linux/MacOS).

Boot the Linux live USB, then open a terminal/shell window
Download and run the ChromeOS device Firmware Utility script using the following two commands (hit enter after typing each command):
curl -L -O https://goo.gl/1hFfO3
sudo bash 1hFfO3
Select option 3, Restore Stock Firmware
Choose whether to restore from a backup file on USB or not
If not, select your ChromeBox model so the appropriate firmware can be downloaded

UPDATE - I think I've successfully reinstalled OpenELEC. Thanks.