It is a lovely collection of herbs and has more than a few variations. It really isn't a thing, but caught on after someone marketed some dried herbs as such. Boom!, it caught fire, morphed a bit here and there and Voila, a mysterious collection of herbs. They are tasty in focaccia and for that reason, I like them.
Very simply, mix all the dry ingredients together and store in an air tight, light proof container. An apothecary bottle is good. If you are storing the container in a cabinet, clear glass from a left over empty spice or herb bottle will do very well.
As with so many things where quantity can be fluid, and this is certainly one of those things, add or subtract to your preference. I really like the lavender flowers, in part because they taste nice but also, because they offer a very nice color to the bread. And, they taste nice.
Did I mention that they taste nice?