Did you start small as can be on cardboard and build up? Some folk build it to completion and then find an extra mounting stud or a jumper in the wrong spot. There is no exact method here outside of starting with as few parts as can be. No case is required.
Just bought components from partpicker.com and built a simple desktop pc, but it won't post. Partpicker noted no conflicts, but motherboard's website doesn't list my RAM as compatible. Which is more likely to be true?

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