This worked beautifully:
https://thesolving.com/storage/how-to-create-an-iscsi-target-with-freenas/
I changed the base name according to RFC 3721 standards. https://tools.ietf.org/html/rfc3721.html#section-1.1
I did however have a problem with Deleting extents. I could not get that to work at all even if I deleted the whole pool. Will have to do more testing.
Check out http://fabozzi.net/how-to-configure-iscsi-initiator-with-chap-in-centos/ if you need to see how to setup CHAP from CentOS
