Windows 11 VirtualBox guest in openSUSE Tumbleweed host

How to install Windows 11 as VirtualBox guest in openSUSE Tumbelweed host. Should work for other hosts too.

Windows 11 arrived early October. Visual Studio 2022 arrived early November. Here I am in the middle of November thinking of taking both of them on a test ride. My Dell G3 and Lenovo Legion are both capable of running Windows 11 but I have no intention of disrupting my current workflow. Not for the next one quarter. So, VirtualBox it is.

Windows 11 and VirtualBox

The first attempt was a failure as Windows 11 refused to install on "incompatible hardware". Found a solution soon enough. If the link goes missing, the PDF should serve as an alternative: