With PC computers, you can probably let your imagination run wild and embed your PC anywhere you like. Such a built-in PC is demonstrated in this example where the author puts his whole desktop inside a drawer.
The server build was completed by fitting the Samsung hard drive behind the power supply. I made some mounting brackets out of right angled metal brackets I found at the hardware store (they are actually “concealed perlin cleats”). They allow enough height for me to eventually add a second hard drive underneath the first, although at this stage that space is filled with the surplus power supply cables.