x2 on the very dark nest box and laying later in the day to evening.It always surprises me to see folks say their Marans aren't good layers; mine are among the best I have. The only thing that frustrates me just a bit is that my flock tends to lay VERY late in the afternoon to early evening. That I find odd. I also have found that they most definitely prefer a very dark nest box. When I moved their nest boxes to a different location, which coincidentally was darker, I began to immediately notice more eggs each day. It's the only thing that had changed; that was 5 years ago, and I've left the nest box in that same location!
(Incidentally, here in the U.S. they are simply "Marans" - not "French Marans".)