As good as FreeNAS has been, most of the clients on my home network are Windows based and speak CIFS/SMB, and I’ve not had great success with FreeNAS reliably/stably serving these protocols. Under load, the shares sometimes lock up and stop responding, and permissions can be a bit hit and miss.
diskpart list disk select disk x clean create partition primary format quick fs=ntfs label="SD" active assign letter=C exit dism /Apply-Image /ImageFile:D:sourcesinstall.wim /index:2 /ApplyDir:C: bootsect /nt60 C: /force /mbr bcdboot C:Windows
I couldn’t get that final line to write to the MicroSD. I kept getting errors about BCDBOOT not being able to write the files, or unable to find the source location. However, I read the documentation about BCDBOOT at Microsofts MSDN site https://msdn.microsoft.com/en-gb/windows/hardware/commercialize/manufacture/desktop/bcdboot-command-line-options-techref-di and happened upon the command for writing to USB devices.
C:Windows /s C: /f
This seems to work fine, and a reboot allows Windows 2016 to boot.