"this part has no metal surface that could act as a transfer medium to, say the copper board."

In that case, you have used the wrong part! :-(

"Is there any common technique for heatsinking such a small enclosed device?"

Well, you can design the PCB with lots of copper near the part to conduct heat away, but that's part of the design process - not a remedial bolt-on! :-(
You still need to do the sums to be sure that the device will be within its specs.