I'm also interested in any insights shared here. I used the same mold, but without an impression. Followed Delphi's firing schedule and used 90 COE glass throughout. My plate ended up with "holes" in 3 out of 4 corners. Next time I use this mold I will
Check to make sure mold holes are clear
Use kiln posts to raise the mold for better circulation
tack fuse the two bottom glass pieces together before final firing
I've included the instructions and firing schedule hoping someone with more experience will have some suggestions to share.
So yeah, in this case probably not annealing long enough. I think there's too much going on with the whole mold & texture imprint thing to anneal for only 45 min. Plus, the bottom got pretty thin, which would add stress.