Great topic, I think about this a lot. If the principle of free association is first and foremost, I think there could be leaders without hierarchy. Anyone can disassociate from whatever is being led or steered if they choose. I can decide at one moment I am following someone's lead, aware the whole time I could act in self-interest by *no longer following their lead* if necessary or desirable. Ideally, in an anarchist community, those around would accept that this is a normal mentality and not try to calcify leadership structures (which always seem to form an authority, big surprise).
That said, there's so many situations in life that don't really require a hierarchy at all, we're just oversocialized to accept them. Re-socializing ideas around free association is a tough sell though, being quite nerdy/theory-adjacent.