I know have some missing documentation, I hope to work on it and make it better.
for your question: EasyNAS can share storage using ISCSI protocol
it will allow to create working disk on the EasyNAS , boot from it and using from the network.
in order for it to work, you need first to create the storage where iscsi files are going to be saved.
so you need empty disk/s and create a Filesystem out of them
the file system can be a standlone disks (JBOD) or a Raid 1,5,6.
every option will give you a different redundant array.
After that is created, you need to build a Volume on top of the file system
the volume represent the logical seperation between shared network folders.
when you have both Filesystem and a Volume under it, you can then run any application that will use this storage including ISCSI
I hope this helps to understand