Someone else here said chickens lay about 25 hours apart, and skip a day when it gets too late in the evening. I've heard 26 hours, and I haven't timed them, but I think that'd be a fun experiment. But I do know some mornings when I come out at 7:15am, there are 3 or 4 eggs in the box already, all still hot. This past week, I've been collecting eggs after work, or my kids get them when they get home from school. We have 5 laying hens, and usually get 4 eggs a day (depending on who is on their off day).
My chickens are 1 year old, so still very young. They definitely sing an egg song. If "sing" and "song" can be accurate descriptions of the cackling clucking bwoking noises they make. There are times when they just get noisy too, and it doesn't seem to be because they laid an egg or are about to; they're just making their presence known. Or begging loudly for treats.
I have only one chicken who lays outside the nest boxes. Twilight (named for the My Little Pony, NOT the vampire books!) is an Easter Egger and she likes to hide her eggs. A kid at my daughter's birthday party found one in the basement window well! I've found them underneath the coop too. All the others will return to the coop and nest boxes to lay, no matter what time of day it is or how far they've free-ranged. Twilight doesn't seem broody, and isn't making nests in the yard, so I think she may just be too lazy to go back to the coop some days. I just keep an eye on her and when I haven't seen her green eggs in a couple days, I check under the coop or in the bushes for stray eggs.
Lastly, my nest boxes used to be filled with pine chips, but then I started bringing home shredded paper from the office shredder, and that works just fine. They took a couple days and a dummy egg before they realized they could lay eggs in the paper (the first 2 days, they laid their eggs on the pine chips on the coop floor), but once they figured out the new material, they were good.
Good luck! I hope your ladies start laying soon!