Personally, I start with lore. Getting some kind of storyline down always tends to help me! Even though it sounds cliche or not right, I still brainstorm ideas and jot them down. I'll take an idea that I like and start looking for characters, regardless of what they really are or "themed" after.

E.g. Time Travelers

I jot some things about it that I already know

- Travels through time

-Can have steampunk or cyberpunk vibes

-cool portals

And then I put my own twist on it:

Say each time a time traveler, travels, they lose apart of their soul

This forces them to go take other souls

This could be very illegal because,,, stealing,,

If time travelers don't have enough soul whilst traveling, the portal their traveling through collapses on itself, going 2D and suffocating the traveler

See? By putting my own twist on it, it sounds hella cool :) will add to this

I usually pick a theme or a few topics to base it around and then find characters I like that could fit in. (Although sometimes I do this the other way around and end up with the characters first, then find things they have in common).

So, we have a fantasy world with dragons. Well, maybe those dragons like mountains, so there's going to have to be a mountain range somewhere. To get the actual world map drawn out, I usually drop a handful of something on a paper and loosely trace around it (beads, rice, dice, whatever) to get a shape for the land areas. If using dice, you can assign a number to a certain feature if you want to and the same goes for bead colors. Or you can just put things randomly like I do most of the time :')

So, now you have land, characters, an idea, and maybe some mountains somewhere on that land. From there, I usually start planning where I want the other places I came up with during the concept-ish part to go and how they would relate to each other. I also try asking some questions about how everything interacts (Would the dragons be near a kingdom? Would the humans try fighting them? What effects would this have? Where else could dragons live? Are the dragons important to the humans at all?) to figure out placement as well as who gets along with who and what groups should, probably be separated. This helps with boundaries.

Usually I stop at the basics (lore comes after the boundaries, since it kind of builds on everything else), but with some of the more detailed worlds I will continue into things like political structures, detailed history (dates, specific events, etc), religion, and beliefs / traditions/ behaviors.

Overall, I can do things in pretty much any order, but this is my usual way. Although I do skip around on some of the more complex ones and come up with storylines first, like some of the others have mentioned.

It's interesting to see how others do this, too :O