When anyone poses the question, “Is my ___ in pre-molt?” We can link to this with the caption, “If it looks like this.” Isn’t this textbook though? Little round mat, all spread out ready to jump into the new clothes. Doesn’t get anymore pre-molt than this. BTW: little G. rosea.
She-Ra, a mature female Kukulcania hibernalis (southern house spider) I've had for over 7 years, was hopelessly stuck in her molt. I wasn't confident that I could help her, because these spiders are so small and delicate when compared to tarantulas, and she had not even begun to extract her...
Eventually I had removed as much of the old abdomen as I could without tearing the delicate skin of the new abdomen. (I'm not sure, but there might still be trace amounts around the pedicel and book lungs.) Then I saw that one of her left legs was still encased in the old exoskeleton.
Having removed the loose, easy sections, I could see that some of the abdomen appeared to be stuck around the book lungs and epigastric furrow. I continued using the water dropper to try to soften and separate.