This was on of my favorites.  Rubik’s cubes make it easy to do a mirror image on the back, but since these are letters, they must read left-to-right on both sides  That’s much harder, so the back side (on the right above, viewed through the window) has many places where there is yellow instead of white or green, and a few orange spots.  That’s all because I don’t peal off the stickers and just put them back on, I start with normal cubes and solve them into these patterns.