Just finished building 2 headphones over the weekend, one with the Symphones Magnum V7 drivers and the other with Nhoord red drivers. A very simple affair, easily the most time consuming portion is the braiding of the cable.
I bought the headphones frames from Taobao and it comes fully assembled. The wood are South Africa Ebony and Rosewood. Each frame is about $100 shipped to Singapore, and come with 2 different set of pads, 3M grills and pads which I didn't use.
The cups are screwed together, with SMC connectors, so it's a simple matter to unscrew the cups, attached the drivers to the cup lids with double-sided mounting tapes (because the drivers are slightly smaller than the lids), solder the connecting wires to the drivers and screw back the lid. At this point, your headphone portion is basically done.
Here they are with the balanced cables attached. I used silver plated wires terminated in 4 pole XLR plugs.