'Setting In': establishing outlines by matching sweeps or slicing. In other projects on Woodcarving Workshops I've levelled the background before setting in. I find that for shallow reliefs like this where all parts have to be quite exact and there are tight spaces and corners, I tend to set in first. However, there's no problem with you swapping stages and levelling the background first.
An important point to remember here is that the drawing is not the carving: let the tools create the shapes and modify the lines.
Another thing to remember at this stage: no undercutting.
(And apologies for the camera wobble around 8:09. Carrie was trying to keep up with me...)