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 https://www.fabozzi.net/how-to-configure-iscsi-initiator-with-chap-in-centos/ if you need to see how to setup CHAP from CentOS