Cut to size the number of jamb legs needed to create the desired amount of shelves. These will be parallel to the legs of the frame-out.
Measure the piece of stained glass in order to build the frame-out within the shelving unit.
Use 2-1/2" drywall screws to attach all four sides of the frame-out and jamb legs, making sure to pre-drill each hole before screwing together. Once everything is in place, insert the frame-out into window opening.
Rip down each shelf with the table saw to mimic the width of the jamb legs, and router each end of the shelf for that smooth, polished look.
When all four pieces are installed, carefully insert the stained glass into the area. Attach the other side of the stopper on the reverse side of the stained glass to keep it in place.
Remove all the shelves to prime and paint your desired color.
Add some trim around the border of the window, and re-install the shelves.