This is a wonderful technique that is so straightforward but gives amazing results!
You stamp a line art image onto a piece of Vellum cardstock, this is Stampin’ Up! heavier weight of vellum and is lovely to stamp on. I use Stazon so it dries quickly and gives a lovely crisp edge. Once it is dry flip it over and using your markers colour in the image from the back. This gives a muted tone to the image and looks just like stained glass.
I have used brads to secure the vellum cardstock to the mat layers and finished with a little bit of ribbon.