If I bought a plot of land and applied for planning then got and architect to design a property, would I say I built my own house if I paid a ground worker to dig the footings, a bricks to back it up, scarky to wire it or do I need to physically lift every brick and whittle the Window frames from an old tree?

I would say I built my own house even if the trades did the grafting.

Same with a car, I would say if you drop your car off at a shop and come back to a finished article then maybe it is bought, if you do what you can and direct other people then built.