For those communities that do already have a stateless, classeless society, you mean? This happens.
The TL:DR is that you function on the agreed-upon principles of horizontality and mutual aid, but I know that doesn't sound like a satisifying answer, and there are so many ways that might look.
In China during the one-child policy, some people had multiple more than just one kid. You couldn't buy that with money iirc. Tbh I don't know much about China's form of communism though
China followed Maoism, which was also an authoritarian state. In such theories, they are "communist" in that they ostensibly seek to progress to a communist society. Tbh I doubt the sincerity of such a pursuit.
There are communities that could be genuinely considered communist in its true form, but people typically don't cite them as examples of communism working since they're not nation-states ... which is the whole point lol