You could use the article I wrote: http://www.fotomozaic.ro/
Your tongue is probably sensitive enough that you won't need to worry about clamps or jigs. At least mine has always worked just fine for work like this. Students of dentistry learn early just how tiny of a difference in height the tongue can detect. I offered to send Canada Balsam to anyone who needed it in another thread weeks ago. When that is gone I also have some very high grade rosin (some from Honduras, some from China, and more from other places). It will work just like Canada Balsam, actually.
If the element is etched on the front surface, you will have a much more expensive and complex repair. Good luck, however.