Glad to hear that Leia checked out fine at the vet. Not sure what you've researched, but I always put this link up for expecting Moms.
Dog Breeding and Canine Reproduction by Debbie Jensen. Dog Breeding and Whelping guide for dog breeders. It's a great site that has lots of useful info.
Good luck on the whelping box. I've seen some members post pics of their set-up here before. Maybe one will see your thread or you might do a search on this site. I'm useless for that as I have my girls whelp their pups in my computer room and I just set up an area in the corner there. Works for me, but most do use some type of box.