As some of the parts have a somewhat small pin pitch and some parts don't even have legs sticking out (RP2040 QFN), going with a stencil for solder application and then adding the parts is probably the way to go.

Base PCB is single sided, and all other components can be handled with a soldering iron (buzzer on frontplate PCB, SAO connector and the OLED screen). The two 2mm sockets will simply screw in to the faceplate.

The 3D printed parts, especially the small buttons and the rotary knob, will need a fairly decent 3D printer. I printed all with a 0.2mm nozzle and used adaptive layer height for the button caps and the knob. The slightly curved top surfaces ends up a bit stepped if not. The small steel ball for the rotary knob notches needs to be pressed into the small hole. It might be a little tricky.

With the base printed and the PCB's soldered, the base PCB drops into the bottom, fold down the screen and give it a tiny piece of double sided tape on top of the USB-C connector to hold it and then add the knob and the button caps. Finish off with putting the face plate on there and squeze it in. It's a tight fit, but should stay put.