The level of abstraction when I started was that you had to solder the components (resistors, capacitors, chips - well IC holders, chips were expensive) to the PCB board - that was "building your computer", none of this nancy-boy rubbish of "plugging stuff together" with "slots that can only take one type of card".

I'm fairly certain I know how it works. Being a physicist helps with the even-lower-level-details if you want to start talking about transistor doping, or electrical circuit theory, for example