I didn't really do any preparation. I had recently been thinking that pretty much every website I had ever built was sadly no longer in existence, and so I wanted to start producing real, "tangible" artifacts from my work; something that might have a shelf life of more than a couple of years. I had those recent SSR adventures in mind, and wanted to write them down before they faded from memory.
I usually begin with a bulleted todo list of insights or topics I want to cover. Then I dive in, and write in a more or less stream of consciousness fashion, which causes me to think of more topics to add to that list. I comb over the article and the list iteratively, reordering stories, editing, and and adding context as I go, until the result feels right. In this case I didn't have any notes, the content was rebuilt from memory.