I thought of the concept for Alice X way back in 2014 I believe, lol! It was such a random idea now that I think about it. In the 2 years until I actually started to produce the pages there was a lot of procrastination. The reason for that came down to writing the actual script. I find it easy to create a concept but when it comes down to actually fleshing out a story...mmmmyeah. Once I buckled down though, the writing of the first chapter took maybe a day with a few hours over a week or two doing revisions (I know, I know...procrastination is a hell of a drug). The full story was also plotted out in a day so it will come down to writing a script for each chapter going forward.
I don't know how other's do their pre-production, but for me, if I don't have a script I will probably run into issues later on. In the entire first chapter I've worked on for Alice X, I have not had to make significant revisions because I did all that revision at the written stage. I believe that a comic is only as good as it's written content. If I take away the pretty pictures, do I still have a competent story?
Once I was satisfied with the script everything else came down to assembly line ease. Using a script format helps me with visual rendering as that format uses visual directives (I do filmography and storyboarding) so going into thumbnails was straightforward and the remaining production just came down to refining those thumbnails as larger pages.