Lay an egg that is!
There are some tricks you can try to get you free range hens to lay in the nest boxes. Most hens will lay sometime in the morning to early afternoon. You can either try to keep them in the run till then and then let them out to free range hoping that most of them will have laid before you let them out. You can also try keeping your hens in the run for a period of time hoping that it will become a habit to lay in the boxes and then let them start free ranging and hope that they will come back to the coop to lay. Another thing you could try is to set our nest boxes in an area you know they like to go to, say the edge of the woods or something, and hope they will come to lay them there. Chickens like a quite safe place to lay there eggs so this may attract them. Or you could just hunt for them like an Easter egg hunt everyday and then guess as to whether they are fresh or not! I prefer to keep mine in a run where I know they are safe from predators and where they can lay there eggs where they belong.