iFixit has done a teardown of the new Apple HomePod and here’s the conclusion upfront: it’s not meant to be opened by the consumer. So pretty much like most consumer electronics these days. End of story.
If you are still curious, this is how it goes down. You first need a heat gun to get through to the screen at the top and the rubber base at the bottom, which are securely fastened with glue. Then after that you find some more screws, then some more glue, then some more screws, then some more glue. At one point, iFixit even managed to crack their HomePod while trying to get through a glued surface and eventually had to resort to using an ultrasonic cutter, which caused some irreparable damage. After all that you do have it open but at that point it’s impossible to go back to the way it was.
Bottomline is, if you have a HomePod and there’s something wrong with it, just take it to Apple to have it repaired. They’ll probably just replace it for you.