Fusion drive unavailable after HD erase
You probably deleted your Logical Volume and the superior  Logical Volume Family.

To create a new one boot to Recovery Mode, open Terminal and simply enter:

diskutil cs list #to get the lvgUUID (UUID of the Logical Volume Group)
diskutil cs createVolume lvgUUID type name size


or in your case:

diskutil cs createVolume C970ADA-0D05-42AA-9E9C-403ED0E5335 jhfs+ "Macintosh HD" 100%