My mirrors can be made to any size. I carve them out of 2"stock and the mirror is 1/4"thick. I also route a channel in the back about a 1/4 bigger than the mirror, which allows the wood to expand and contracted without affecting the mirror.
#705M Ash (outside Vinegar wash)
#707M Ash (outside Vinegar wash)
#708M Poplar (outside dyed brown)
#710M Ash (outside Vinegar wash)