There are a few lingering questions pertaining to the FlashSideways Timline (FST) that I think have been overlooked, or simply not answered. The most imporant of these questions for my understanding of the show is:
How did the Losties create the FST?
To find the answer to the creation of the FST, I will first investigate the conversation leading up to Sawyer and Juliet's reunion in it. Sawyer is trying to get a stuck candy bar out a vending machine. Juliet walks by. After a little banter, she tells him a secret "If you unplug it, and then you plug it back in again... the candy just drops right down." How does this relate to the Island? The action that Juliet is describing with the vending machine is analogous to the actions performed by Desmond and Jack with the Heart of the Island. Desmond unplugged it (although in this case, it was a giant stone and not an outlet, but both served the purpose of powering down the object) and then Jack plugged it back in. But what was is the proper analogy for the "candy" in the Island situation? This answer comes from Mother's description of the Heart of the Island as seen in Across The Sea. We get a very short description of the Heart when Mother passes on the protectorship to Jacob. Jacob asks her "What's down there?". She replies "life, death, rebirth". That is the "candy" in the analogy. Through the process of unplugging and replugging the Heart, Jack and the Losties were able to aquire its candy, that is, rebirth. Perhaps as a reward from the Island, or by sheer force of will, the creation of the FST was due to the powers of life and death trapped in the Heart of the Island. Releasing them for short while allowed them to be manipulated into a Universe of rebirth for the Losties.
Any questions?