In a comment, Bonfieldjane asked why Japanese embroidery stitches the foreground elements first when most other embroidery techniques stitch the foreground elements last.
In Japanese embroidery the elements of a motif, such as the petals of a flower, and individual elements are defined by leaving a small gap between the stitching. This is called a one-point open space and is one of the things I find most difficult to control. The gap should be big enough that the shapes are clearly defined but not so large that they look clumsy.
The upper elements determine the shape of those behind them, not the other way around so it makes sense to stitch them first. This is particularly so with heavily padded embroidery. In the picture below the uppermost petals have been padded and stitched, they determine the placement of the padding for the next layer of petals.
The stitching on these petals fits around the (hopefully) perfectly shaped top petals.
Of course, there are always exceptions to every rule and I will learn about those in later Phases. If you can't wait 5 years (at my current rate of progress) for me to reach Phase IX, you can read why Jane is stitching back-to-front in this post.