To make a circle hole in a curved surface, the easiest way is to hold your circle template (deck plate or circle template form) over the curved surface.
Then take a pencil an trace around the circle with the pencil running straight down on the curved surface while holding the template flat as possible.
If you rock the circle template down on each side to the curved surface, you will end up with an oval.

danperry - how did you make your glass recess?