I put it on gumroad and sell it as a digital download. 100% DYI. The sales come mostly from my social media audience.
Building the audience took about a year and a half. But what made it easier is that I didn’t set out to build it just to sell the course, it was mostly a byproduct of trying to form connections and get more awareness for my startup. Then the course was just a way to capitalize on it even more.