I designed this mini-itx case for the Asrock IMB-1212 motherboard.  It only uses the CPU fan and stays cool.  I have included blanks of the front, top, and IO panels so that you can make this case work for your specific motherboard.  The profile I uploaded will make the side of the model that is face down appear to be almost injected molded.

BOM (will update with more detailed version soon):

22x - Screws

1x Double Sided Tape

WARNING: While the motherboard and CPU stays cool on my motherboard it is a low energy board and I cannot guarantee that a more performance oriented motherboard would not get too hot.