Linking to that excellent article by Ursula K. Le Guin on plot reminded me to look through some more stuff on her site. Here is an open letter relevant to worldbuilders, called Plausibility in Fantasy. An excerpt:
For example, Tolkien’s references to places, people, events (often of long ago) that are not part of the immediate story: these give the reader a conviction of the reality of the immediate scene — because it is shown to be part of a much greater landscape, a long history, a whole world of which it is only a glimpse. This is a strong technique for making an imagined world plausible. This is a technique which one can imitate, performing it in one’s own way.
Now, with Tolkien, that history and geography already existed in his writings before The Lord of the Rings. But in my fantasies, I have often mentioned events or places which I didn’t yet know anything about — for example, some of the later exploits of Ged mentioned early in A Wizard of Earthsea. These were, when I wrote them, merely words — “empty” nouns. I knew that if my story took me to them, I would find out who and what they were. And this indeed happened…
On a related note, I find it much easier to work on parts of my conworld that have connections with cultures I already know of. For example, the cultures of the continent of Kraya are all still very vague because they are so remote from the Odiran cultures. They had essentially no connection at all with Odira until just a few centuries ago, similar to the disconnect between Afro-Eurasia and America on our world. Perhaps, like with Afro-Eurasia/America, there might’ve been a few visits before the start of prolonged contact, but nothing with much in the way of lasting effect. And so, nothing I try to figure out about them feels right. It all feels very … arbitrary. I only know of a few vague details about one of their cultures, and only from the POV of the Kasshi colonizers which, obviously, is far from unbiased, but may be a start if I can figure out what of those are misconceptions or outright lies, and what are based on truth. That might give me a foothold to start figuring out more.
Le Guin on Plausibility in Fantasy