If you were to take a large enough sample of writers, you would probably discover that every possible starting point has been tried, and worked, for someone. Every storyteller is inspired in an different way from every other storyteller, and differently for each story. Every story is discovered via a new path that has never been traveled before, and will never be traveled again.
When starting a new story, game, etc., hopefully you have some starting point - an idea, a theme, a character, etc. Take your starting point, and ask yourself what that starting point requires. A character who is wizard is going to need a magical system in which he practices and a history - parents, birthplace, etc. A theme implies an appropriate conflict, which in turn requires a set of combatants and a context.
As you start to fill in details, it will be like tracing the components of a tree. If you start with a leaf, you will trace it to its branch, which will trace back to a larger branch, and so on until you eventually find all of the other branches, the trunk, and the roots. If you start at a root, it will lead you to a larger root, and then a large one, until eventually you find all the roots, the trunk, then the branches and the leaves.
My ideas are usually something along the lines of "What would happen if there was a person X living a world Y?" Where the properties of character X and world Y are defined only in the very broadest terms. From there, I can usually figure out how the story is going to end. Everything else must follow logically from those starting conditions to make the story interesting, compelling, and inevitable.
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possible duplicate of How can I break down the task of creating a world into manageable chunks?
– Styphon – 2014-09-19T19:58:13.7401@Styphon I strongly disagree. Our questions are quite distinct. Your answers do not suffice as answers to my question and my answers do not answer your question. Your question speaks of an organizational process of design. Most notably how to disassemble and later mesh all the puzzle pieces. My question is asking about what is the easiest, most basic building block. If my question is a duplicate of yours then surely yours should be closed as "too broad." Closing mine as a duplicate of yours would require closing ALL questions about non-specific design planning as duplicates of yours. – Mark Balhoff – 2014-09-19T23:02:00.337
I'm not quite sure about this question, but "which is the most natural / easiest foundation to establish first?" honestly seems rather opinionated to me. – a CVn – 2014-09-19T23:26:20.670
1@MichaelKjörling I see where you are coming from to an extent but I don't see this as a completely subjective or open-ended question and the answers have all pointed in the same direction. It is a narrow question that partly operates on the premise that all worlds can be objectively boiled down to the same core components that overlap in the same general manner. That objectivity about how the layers co-exist is the core question. Having any subjective element to the question would make World Building an extremely narrow site that wouldn't make it out of beta. – Mark Balhoff – 2014-09-20T00:01:17.373
1Maybe [edit] the question to ask whether there are dependencies, such that X always depends on Y (and thus designing Y before X is a good idea in order to have a consistent world)? That should, at the very least, do away with the opinion-ness, without invalidating answers already given. – a CVn – 2014-09-20T17:09:02.550