Man, I just played your game and was blown away. Your process definitely worked out for you! Definitely makes my list of favorite game jam games I've played so far.
I'm not an artist, but I think my process is somewhat analogous to sculpting something out of a block of marble. You have an idea of what you want it to look like and begin chiseling away. As the marble begins to take shape, you refine it more until you've made your sculpture. I'm sure there's more to it than that, but it seems close enough haha.