Or rather which side of the hard disk produces the most heat?

sorry guys, i just had to ask this question (although it sounds dumb) ...
i do not have any thermal probe, so i cant determine which part of these:
TOP, BOTTOM, OR SIDES?

i couldnt google any details regarding this matter, as if there's no one ever raised it yet (maybe i'm the weirdo)

i'm hoping if anyone who had the previous knowledge or a thermal probe and curious enough to test it