Monica commented that red liner tape might work for my letters ... I used a double sided sticky tape, but with the narrowness of the letters, it was difficult to apply, so I had switched to a liquid glue. I also was cutting the letters with sizzix dies in my cuttlebug which is rather challenging, so I still don't think I'll ever do this again!
This is one of the cards I rejected before completion, then decided today that I should at least finish it for personal use.