Hey Dave, This is what I do. First, I make my own frames so I don't have to fit the portrait to the frame. I prefer a wood backer, so I usually use stained red oak plywood pannels. I don't like to stain the Baltic birch but rather use the boiled linseed oil mix. If you are buying a frame, you need to mesure the thickness of the portrait and backer board, and make sure the rabbit in the frame is thick enough. I dont use glass in the frame, I like the portrait to be exposed.
This is how I do it, others will come on and explaine how they do it. Just pick what sounds good to you!