I have been into worldbuilding, drawing maps and stuff, since my late childhood, and also later on. Some were used in homemade RPG's, or custom maps for diverse game mods (which have been lost and not been released in general).
At some point, during maybe 2 years, I also had very lucid dreams that were happening in some fictional world that looked a lot like the real world where I lived (Western and Central Europe) and there were connections between different places in different dreams, sometimes I dreamt being twice in the same imaginary city with the exact same features during 2 different nights... and well somehow I managed to connect all these things and to map the world I was dreaming about, and this was for example the base used for the city of Mist.
So I can say that some imaginary land was imagined by me (Aldland area), while some other parts (Maritime-Romandia) were in me and I've seen them in my dreams very clearly. And some parts are actually made from scratch, specifically to fit within the OGF world, like Brevinia which relates to neighboring Karolia, or Boscunis which was made to fit within the Neberly design all around.
I created this country of Älvedic Confederacy (obvious reference to Helvetic Confederacy in the real world) from bits and bobs of what I can remember of these imaginary worlds, with some adaptation to OGF's constraints, like the fact that it takes place in a modern world context with Eastern Ulethan cultural aspects.
At first I used mostly random generators I made myself in PHP, but sometimes there can be a hidden meaning in one name or another. But when I had to "conlangify" the thing, I actually made up some languages out of Proto-Indo-European resources and added German, Baltic, and English influences (because of Mergany, Keira, and Neberly proximity).