I also have an egg every couple days that's on the floor, or just outside in their run. I swear they just get a kick out of making me go fetch the eggs. We put wooden eggs in our boxes because they were eating eggs. It was a 100% instant cure for that, by the way. Having the wooden eggs in there certainly helped though. I had a couple golf balls in there before, and would get frequent ground-laying episodes. Since wooden eggs, it's 99% in the boxes. Worth a try.
Far as boxes go, we've got 6 boxes for 17 birds; however, one is a silkie who probably needs a box close to the ground. I just don't have on in there, because I'm pretty sure it's easier to pick up one tiny egg from the ground than it will be to collect 16 eggs a day from yet another box that they will squawk about. They use all 6 of the boxes, but there are three favorites that get the most eggs and the most amount of squawking over whose turn it is.
