Stephen Lujan
Sorry to be so contrary, but this image not at all analogous to the industry meaning of "vertical slice." Working by vertical slices is the opposite of starting at the beginning and grinding through in a linear fashion. Its the solution to the problems that emerge from that kind of development. A vertical slice is a working feature that adds value to the end product. It would be akin to the artist painting the face first,  a complete feature of the greatest value to the end project.