You might want to consider using perlite in the lay box, rather than covering the whole cage with it. Personally I prefer coco fiber, but to each his (or her) own.
I suggest making a laybox using a tupperware container and just cutting a hole in the lid. I use peat moss- that I kep moist but not wet or damp- in mine and that's what the gecko's lay their eggs in. Then I take the eggs out and put them in a deli cups that are 3/4 filled w/ very slightly moistened perlite or you can even use vermiculite- either wil work fine, but for using perlite for a laybox for your gecko's I don't think they'd like using that and if they don't then you wont get as good of breeding results! This has worked great for yrs. plus my leo's love the peat moss b/c when it's just right it's really soft dirt that they slightly sink in when walking through and they love to dig. The peat moss hide also just works great as a humid hide and what I use for my other leo's too not just breeder's.
I do have just a couple pics that are on my site if you want to take a look go to my care sheet- I really need to put alot more on my care sheet! But it does show a couple pics of my breeder's lay box and another of just a humid hide that just a male had. I also need alot to do on my site, info, pics etc.. I know. And in one of the pics the peat moss is too dry! So that's what it look like when it's too dry and when like that you can get dented dried up eggs, even though some can be saved, you don't want that! I hope I helped! If you have any other questions I'd be happy to help just email or pm me.