I am building a program for my current workplace, and the tasks and categories are unclear. How do I set up a work schedule for myself to get some flow, instead of being choppy and distracted?

I'd say first figure out the goal of the program. Knowing what target you are trying to hit helps you take steps towards hitting the target. Then I'd say set reminders that you are doing this for a reason that helps you come to life and when you are doing this project you are doing something you really love.

I would make a list of the tasks and categories with timelines and prerequisites attached to them. For example, I have to do x task before y task. I like to use excel for this type of listing. Maybe you can use a project management program or a gantt chart.