When i do mine i just lay them on the backing i'm using and glue them to that. Sometimes i buy frames with mirrors in them and just use the frame for mosaicing.

I use the router to make a place for the mirror, then cover the back with masonite or cardboard to prevent scratching the mirror. Good luck. Carol

OK, let's just let this one sl-i-i-i-de on down the page while I sit here and douse my flaming cheeks! We don't really need to talk about how long I spent trying to figure out how to inset it without a router or how to accurately cut a filler piece to go around the mirror before backing it with yet ANOTHER piece of wood....BROTHER! Oh, well, DH swears I simply HAVE to complicate everything...maybe he's right- not gonna tell him, tho! Thanx, gretch, for laughing silently!!

Pat (who feels really stoopid LOL!)

Never made any myself,have only bough mirros on sale ..but i know bama glues her's on the mdf or plywood she's using.I think she's gone but she can verify when she gets back.

LOL - I'd say there are several ways to treat a hand-made mirror base. I've just cut the base, then placed the mirror and surrounded the mirror w/tesserae. On Frame for Frog Prince, I built the frame around the painting, then placed the whole frame on a piece of plywood, thereby leaving the opening for the painting to be inserted into that space. Both were super easy. I have three routers in the garage workshop and don't know how to use a router YET!!!. Got promises from handyman and a friend for a lesson in learning, though - when time permits.

I sooo wanna learn to router too!!! Just another thing to add to the list!!!