Where do I find it?

Open the BookyAI app and click "Activity" in the sidebar. The Activity Studio page shows all the studios. The Mazes card has a picture of an open book with a square maze being solved in pencil and a round maze, and a fox-shaped maze beside it. When you own the studio, the card shows "Yours" and "Open the studio". Your books are listed under "Your activity books" on the same page.