The wood pannel and hourglass are from a thrift shop. It used to be a "funny" (in the funny / stupid uncle way) sign on which the hourglass was used to monitor time limits on the phone with your mother-in-law, your mother, or your grandmother. 

Sketch (well, kinda) and final (well, not really) product

Insight. We did not want the sign to sound to much like a boring lesson.

Instead, we wanted make it sound a bit more like a game, a challenge.

Note to self: I will never paint on rice!

Voilà!