You might be impressed by the underglaze decoration, but I am more impressed by the transparency of the clear over glaze. This type of decoration is quite easy to achieve at low temperatures, like cone 04, but much more difficult at medium and higher temperatures. That is why many people shy away from this type of decoration, they have bad experiences with clouding in the glaze that obscures the design. Because a lot of work goes into the design, one wants assurance it will not be ruined in the glazing and firing process. Reliable transparency is a combination of glaze application thickness, glaze recipe, glaze materials, firing temperature and firing schedule.
A ceramic compound meant to be applied to green or bisque ware and covered using a transparent overglaze. There are good reasons to make your own underglazes if you are in production.
Every glossy ceramic glaze is actually a base transparent with added opacifiers and colorants. So understand how to make a good transparent, then build other glazes on it.