My daughter's dragon used to dig frequently as a juvie, here and there, but I would say that a sudden interest in digging in a CWD old enough to be gravid should be taken as a possible signal before oviposit. If you have suitable substrate in your set-up to satisfy her egg laying requirements then you don't need to add anything further. I went ahead and added an egg-laying box to my enclosure just because it would be so much easier if she would just lay them in there-however, mine has expressed no interest in digging in the box-right now she's digging UNDER it. LOL Mine has been digging for several weeks now, so the ovipositting will not happen overnight. Good luck!
My Dragon Kingdom
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dianedfisher@yahoo.com

My 3 CWD-Avanyu, Tripod and Drago