I had some 1/2" T&G wood sitting around from a wall project and, in furtherance of the concept are, for the most part, a myth, I incorporated the pieces into this frame.
Both the inner and outer frames are just from 2×4 material cut down to 2×2 and rounded over using a 3/4 radius round-over bit.
The outer frame has a single rabbit on the inside, to accommodate the T&G. The inner frame has a rabbit on both the inner and outer edges. The outer for the other end of the T&G and inner for the picture.
This was a big frame, measuring about 30" x 55"
I apologize for the quality of the photo. It’s about thirty years old.