Good question. I would do two things: (1) Make sure one of the five story tags is "satire."

(2) Optionally, you could add a kicker to the headline. This is the optional all-caps grey test that sits above the headline. Most people don't use it (I rarely see it), however it's works for adding a "SATIRE" disclaimer since it sits at the top and doesn't otherwise mess with the body of the story. We occasionally use this in Slackjaw pieces.

Philosophically, I dislike it when the main body of a satire piece has any kind of authorial/narrator intrusion that tells you about the satire (unless it's some intentional meta joke)

Kicker info:

https://medium.com/blogging-guide/medium-kicker-f203a2cb2f75