(top) A rough layout - Used as reference by the animator.
(center) A color sketch... used as reference for the background painter.
... And the final background painted by artist Phil DeGuard referencing Maurice's final pencil layout, as well as the color sketch.
This background was then tested under camera with a simple character cel set-up. The resulting film frames were reviewed by Maurice to see if everything was working. If you look closely you can see the grease pencil line Maurice made through the above rejected test. He made changes to the set-up and re-shot it. Once everything looked ok... he proceeded to design and test the rest of the film.