Exactly as written.
I mean using the techniques of additive manufacture to literally lay down electrically conductive traces and pads using some sort of spray, extrusion, direct transfer, etc. I have the sense that laying down a conductive layer of some thickness around 0.1mm might be possible these days. Surely it would only require a thick conductive ink in an inkjet with a modified nozzle. Allowance could be made for variations in conductivity and inductance relative to copper. Laser sintering can 3d print metal. It does not seem a million miles away to sinter a flat pattern on a substrate.
There is the issue of soldering, but that would be okay with a metal medium. There are silver conductive paints currently in existence. An who knows, you only solder pcbs because the pads are there before the components. What if it were the other way around and you formed the traces over the component leads?