A quick outline is absolutely all takes to set up an entire course. Start with a simple list of section headings:
Literally write down only the headings that come to mind, nothing more. This takes only a few minutes.
Once you’re done, revise. Make sure all the needed sections are there, change the order, remove anything unnecessary, combine sections when that makes sense (like “broccoli and cauliflower”!).
Imagine that each section contains about the same amount of info. If it seems that a section will be really long, divide it into two or more sections. Short sections are good for holding attention.
That’s a first draft! It can take as little as 30-60 minutes in total, including taking a break, sleeping on it and checking it next day with fresh eyes.
First draft: done.