Hey John, First, Like Al W, I don't like to use glass. And to keep it simple, I use a stained 1/8" oak plywood as a backer board. That makes the total thickness 1/4". I make my frames simple too. If you have a table saw and a dado blade set, or a router, you can make your frames. I usually use 1/2" to 5/8" thick wood to build the frames. Anywhere form 1" to 1 1/2" wide. I use a miter sled on my table saw to cut the miters, but you can cut them with your miter guage. I cut my rabbits (thats the slot on the edge of the board) with a dado set on the table saw, but it can be cut with a router and a straight bit. I don't cut any profiles on the frames but I do round over the outside edge. Like I said, I like to keep it simple, so I don't reinforce the miter joints. I glue the portrait to the frame and the backer board to the portrait. That way the frame becomes an integral part of the piece.
Here's One I did back in November. Pattern by Grampa.