Install going horribly wrong somewhere - mountroot problem followed by GRUB rescue

So, to begin with I am completely new to FreeNAS and *nix in general and unsure what I'm doing wrong to get these problems.

I've downloaded the latest release of 11 to install. Currently I'm downloading 10 to see if that may fix my error separately. However, that aside I've set my mobo to boot from USB. I has successfully detected both the boot USB with the iso written to it and the empty USB that I intend to install to. The iso was written with Rufus as an ISO not as a DD.

I've booted...

Install going horribly wrong somewhere - mountroot problem followed by GRUB rescue