If someone is already setting up Windows manually themselves, I believe they're already at some level of technical ability.. but as I pointed out in another comment, my reply was specifically to OP who I made an assumption had some technical ability given that they're here on hacker News. Maybe that assumption is wrong and I recognize that.

That said, the process is:

1) while installing Windows press shift f10

2) a command prompt will open and you type OOBE\BYPASSNRO

When you hit enter the computer will reboot and allow local mode.

I fully recognize that this is a hidden option that most people don't know about, but if you do, it seems pretty straightforward to me for someone that's already at a level where they're comfortable manually installing Windows, but I recognize I have an blind spot due to my own technical abilities.