FreeNAS - remounting a broken SoftRAID

In FreeNAS, I stopped my RAID by removing one of the disks. It caused great consternation when the mount point dissappears and you get various warnings across the UI, such as:

Disk management

and:

Mount point

and the RAID shows as "Stopped". Attempts to restart it fail.
Browsing the disk using the File Manager did not show any data at the mount point. At this point the panic set it as I thought I had lost my data.

However, all is not lost. You can still access the data. The mount point just needs re-adding.

I deleted the RAID (Disks > Software RAID > Delete) - ignoring the warning message.

Then select the individual disk and re-add the mount point.