An "L" shape bracket was not required for this specific installation. The quartz material was fabricated to be placed upon a plywood fabricated substrate "box", secured at each end to the vertical millwork panels. The quartz counter floats away from the rear wall, with the mirror panel placed on top of the quartz counter surface. The mirror panel also floats off the rear wall to conceal vertical light strips that illuminate the rear wall finish.

Thank you so much. I will have my contractor spec out the box today!