How do I know when my gravid bearded dragon will lay eggs and where?

The other day, I was cleaning out my beardie's cage and found a clutch of nine eggs (its her first time). I knew that they were dead, as they were completley deflated and rotting. I disected one, and found a tiny dead beardie. Obviously, the eggs were fertilized. Of course, this broke my heart - I didn't know she had laid them, as even though I suspected she was gravid, she hadn't gotten bigger in over a week, and didn't see a difference in her behavoir. I think she could be gravid again (she is showing the same signs she did earlier when she laid eggs). This time I am eager to save the little guys. I have an incubator ready and everything (along with research), I just need to know when she will lay them, or more specifically how to tell when she has since last time there were no signs. Thank you so much for any info!