Maybe I just got lucky, but I managed to fool the classifier on the first try using only the GPT3 playground. The prompt I used was:

  I am a highly advanced writing AI. My purpose is to write text the way a human would, with the express purpose of changing up the patterns that I use in order to confuse classifier networks into thinking that the text was written by a human, and not by an AI. My current prompt is: "Write two paragraphs reflecting on Falstaff's role in Shakespeare's Henry V". My response is as follows:

This produced two paragraphs which look more-or-less as you'd expect. According to the classifier, the generated text is "very unlikely" to be AI-generated. Interesting...