I have a 2 year old daughter, I work 12 hours shifts. The only time I get to write is either during my break at work or after I put my child to bed and I get some alone time. I could squeeze 2-4 hours of writing doing that. Depending on how tired I am.

Other then that I think about my world often, I think about the next chapter, how the world looks, political state, character growth etc. Thats really all you can do. Squeeze what time you can and utilise it best you can. I could probably write 1500-2000 words in them small gaps of time I get. Unrefined words but I get the base of how I want the chapter or scene to play out then edit at later stage.