trust me she will find a place to lay if you provide it, sometimes it may take her a bit to find it but she will just find it, make sure and put vines and stuff going to the lay bucket, and once she uses it once next time she will go right to it the first time, at least thats how mine worked... when shes ready she will go straight to the bottom of the enclosure and dig even if there isnt anyhting there, make sure its clean down there...
IMO depth is everything, not surface area, just a heads up, i use a 5 gallon bucket filled to the brim and she still digs till she cant anymore and lays on the very bottom, its cool when you see them cover it all up mine makes the hole surface on the top of my bucket 100% level, never seen such precision, haha... its cool
best way for me to tell mine is gravid as mine doesnt turn black at all, is she will run circles around inside her cage over and over and over all day long for a few days maybe longer, she gets insanely active looking for a mate...