Let's see if I understand: Long shadow can be done any time of day, but requires a flat surface. Short shadow takes more time and has to include local noon, but does not require a flat surface. Did I get that right?

My question about noon was in relation to the "long shadow" technique, not the "short shadow" technique. I was wondering if "long shadow" gives you a true E/W line regardless of the time of day (or is it more accurate at, say, noon).