What is the flour challenge?

The "flour challenge" is not a well-known or widely recognized challenge. It's possible that you're thinking of a specific challenge that's popular within a certain community or group.

To help me understand what you're asking about, please provide more context:

* Where did you hear about this challenge? (e.g., social media, a specific website, a friend)

* What are the main aspects of the challenge? (e.g., what are people supposed to do with flour?)

* Is there any specific name for this challenge? (e.g., the "flour bomb challenge", the "flour art challenge")

With more information, I can hopefully give you a more helpful answer.