They coat the chips in some sort of coating that insulates them.
My first inclination would be to get the biggest heat sink I could find, fasten it to the motherboard, and build a 12V to 5V and 3.3V DC-DC converter (and 1.8V, if needed). By not starting from 110VAC, you can cut the PSU heat to a level that might be manageable without fans. Then get extension cables for any connectors that you want to keep usable, along with a couple of heavy gauge wires for your 12V leads, stick the whole thing in a plastic box or bag with the cables hanging out the top, and fill it with epoxy....
Mind you, such an approach is almost certainly not advisable, but that would be my first inclination.