This is for Windows 10
I'm pretty new to VirtualBox, but I got the idea that maybe I could :
Is that possible? - and how do I make it happen?
Your desired approach is not impossible, but extremely difficult: on installation, Windows makes itself comfortable for the chipset and capabilities of your motherboard and other non-Plug and Play hardware, the details of which remain undocumented.
If you make drastic changes to this hardware, especially by moving from virtual hardware to physical hardware, it is very likely that Windows will not have the right drivers available or registry settings set correctly to start the system cleanly.
However, you can still use tools designed for making images for quick installs, as this is done routinely in enterprises. See Windows Imaging and Configuration Designer, Microsoft's provisioning tool for Windows 10.