The dies themselves are "assembled" - cut from the wafer, bonded to the wires (or solder bumps) that carry signals to the rest of the system, and packaged for physical protection and thermal management.
In recent times, multi-chiplet architecture has added its own layer of complexity to that process.
We've had to ask you this before (https://news.ycombinator.com/item?id=35998957), so if you wouldn't mind reviewing https://news.ycombinator.com/newsguidelines.html and taking the intended spirit of the site more to heart, we'd be grateful.