Every story needs its own world and, if you're writing fantasy or scifi, that world has to be built.
I started Structures of Earth not quite two years ago, then put it on pause to write the Chained Adept series first (see background). At the time, I had a vivid image of the river town where the action was happening — the capital city for the country in which the story is set, rather the way London functions for England.
But where was that country, and what place in what world did it occupy?
One thing I learned from The Chained Adept — it's fun (and not too hard) to build a world map for a series and much better to do it at the start rather than to try and retrofit one after most of the story is done. That way, the “real world” constraints can ground the story and drive some of the plot logistics issues.
The world of The Affinities of Magic is a new world, and it needs its own maps. I took Fractal Terrains 3 out for a spin last night and started seeding the world settings until I found one I liked.

Here's what that globe looks like if you unroll it, with a pointer showing where my temperate northern hemisphere initial city is located. (I haven't designated any national/imperial boundaries yet.)
One thing is already clear — there will be large differences between the cultures on the inner sea and those with access by water to the rest of the world. That inner sea may be 4200 miles wide, but it's still a restricted body of water, warm equatorial water, and the ecosystem in and around it will be unique.
See? That's something I didn't know before I generated this map. Hadn't even thought about it.

I knew that my primary setting would have a hinterland of grasslands and mixed terrain, and the pointer shows the harbor mouth. If you continue northeastwards, it's 1300 miles until you reach the first of the large lakes — the distances are deceptive.

The capital city is situated at the last widenings of the river before it begins to broaden beyond the ability of bridges to cross it. It's navigable to ocean ships all the way up to that point. You can see the nature of the terrain at this scale. Once I start scattering towns and other landmarks here, I can begin to create a thriving nation with a vital economy, one with a desperate need to understand the magical technology that underlies so much of its prosperity.