Will my custom flag read correctly from the back?

It depends on how the flag fabric is printed. One-layer single-sided print (Type A) and one-layer double-sided print (Type B) show a mirrored image on the back. Constructions with a light-blocking layer - 3-layer (C), 2-layer with blockout coating (D) and 1-layer with blockout core (E) - can be printed so the back reads correctly. See the Flag Fabric Guide for diagrams of all five constructions.