I've built the case insofar as it has six sides and a motherboard tray, but I have no idea what most of the fixings in the DIY pack are for - is there an assembly manual?
Apologies, I still didn't find the time to prepare a separate instruction for the DIY edition but I'll send you the manual for the "normal" BIG560 later.
The build process is similar like in below video, except that you don't have the additional fan/rad brackets - so in the last step you'll have to remove the top and one corner profile to get the last side panel assembled.
I always include more screws than necessary, so don't worry if some are left after putting it together. Btw, the long standoffs, plastic spacers and screws are meant to fix fans at the bottom with some offset.
Any questions, just let me know