I have my windows 10 upgrade fully installed and configured, and all my applications etc. installed.  Now I'd like to generate an ISO file of the installation so that if I have to reinstall from scratch, I won't have to go through the double install (i.e. first win 7 then the upgrade, then the applications).  I know how to do it in Server 2012 R2, but not in plain Windows 10.

When I ask Cortana, she just returns a blank look, as though she's never heard of an ISO file.  Could someone please tell me how to accomplish

You probably need to back up the whole boot drive as an image not an ISO...

If you're looking for a full-image backup, you'll need a third-party program such as Acronis True Image 2016.