How do/did you start planning your novel?

Of course, an idea popped in your mind out of nowhere, but I am asking, do you make the characters, and their motives, and then craft a world around it. Or the other way around? Make a world, and drop you characters in that world, then plan their journey?

Because I did the same, I have crafted a big world, it's big and rich. I have been writing the world for last 2 years now, I have written the lores of main specie of my story, the Giants, and a lower specie, Humans. Lol, in the flow of expanding my world, I said that Humans have existed in that world for only last 8000 years. They came from another planet. But, i don't know if everything will go into the story at one point. Since, humans are lower specie, they are a cattle for giants.

Though, the whole meaning of the story cannot be written in a plot, i'll say, I am heavily inspired from novel series like, Wheel of Time, First Law, and A Song of Ice and Fire, and I have also integrated Moral dilemmas, like the ones in (spoiler)Attack on Titan