Comment by lax4ever

The simplest remaining way that I am aware of is actually an autounattend file. This is a Microsoft supplied method that has been around for a long time and something that I truly believe will stick around untouched because it is pretty much a requirement of any enterprise Windows deployment.

Not only does it allow you to create a local admin account, but you can also skip all the other setup screens that you want by pre-supplying values. Throw this file into your Windows boot media, do a fresh install (which you should be doing when you get a new machine regardless), and away you go. I use this both personally and my work environment. Not only are you then not relying on modifying OS ISO's or compilations, but an XML file is relatively easy to verify that only the settings you have set are the ones being input into the system if you utilize a third party tool like the one available at schneegeas.de