What’s your topic?
If you’re still searching for one, search for keywords and google trends to create content that is actually searched.
Write it down. First a structure, the title and subtitles, then the sub-parts and the key learnings.
Write a full script or simply bullet points, the important is not to feel rote or robotic.
And remember that you don’t need your course to be over 15 hours long. On Skillshare for example,
for maximum engagement, they recommend you to create an around 40 minutes one.