Hi was wondering if anyone could help. I was trying to make a frame for the lithopane. I have made the basic frame but how do i size the inner opening to fit the 4x6 carve. I was trying to place a recess of 1/4 inch on back side so it will sit inside the frame opening but not covering the carve. I have designed the rest of the light box for what i want to do but this part has me stumped any assistance or tutoring would be most appreciated. My idea is to see the carving sitting in the frame and i would resize it to what ever size carving i wish to do.