In theory, laptop manufacturers that use aluminum in their chassis could just put the CPU die right up against the chassis, Remove the bottom feet, and then tell you to only ever use it sitting on top of a table designed to function as a top-down heat pipe (i.e. the kind they use to make “scraped” frozen yoghurt.) The table would become the CPU’s direct-contact heatsink.

Not practical at all, of course, but this is well within the laws of physics. (And people do lesser things all the time, using e.g. those laptop “cooling stands” with clearance and fans built in.)