This tile uses a basic technique referred to as a Zenbutton. CZT Marguerite Samama is credited as the inventor of this technique. She was experimenting with methods for using Fragments in different ways when she discovered it.
You can watch an instructional video, created by Melinda Barlow, CZT, here, to see the basic technique.
I’ve been thinking about trying it for a few days. Yesterday, I sat down and went for it.