Unfortunately I couldn't find an easy way to boot from the USB drive that FreeNAS was using. So I had to use a normal Hard Drive. The only one I had spare with SATA was a little 2.5" laptop drive. That is fine, except I don't have 2.5" caddys for the bays in the front and I can't see any other spots to put this. So I've attached it to the backplane and you can see to do that it couldn't be sitting right on the bottom of the tray. However if I left it like that there could be problems with dust or rodents. So I slipped a normal caddy in, lifting up the front of the drive a little to slide it under.
So sometimes you can get away with doing something without having everything perfect. So don't let the fact that it's not the best way to do something don't let it stop you from doing it.