Although I have nowhere near the ability of some, I would like to offer a suggestion for anyone making the "O Holy Night" pattern or any similar type.
Instead of cutting the outside of the pattern first, as Steve suggested, I cut all of the inside work first. Then paint (or not) the backing and and glue it to the pattern.
That way when you cut the outside it, will then be perfectly attached to the front without the worry of it slipping while gluing. If the backing was the same type of wood as the front, the seam is almost invisible.
Hope this helps.