I intend to install wainscoting in my dining room. Presently, the room is traditionally finished with 1/2" sheet rock and electrical outlet boxes were appropriately installed to the rough framing prior to the installation of the sheet rock. Now the wainscoting will extend the finish surface of the wall another 1/2" beyond the face of the existing. What is the appropriate solution to 'extending' the electrical boxes to make them compatable with the new finish surface of the wall?

Thank you