So Guggenheim confirmed that there will be flashbacks in the next episode of Arrow. However he confirmed that it will be on the island. So we are still not done with it, even though it looks more like a crater than Lian Yu. I have my own theories on what these flashbacks will be about.
1. Flashbacks to the recent event
So my idea for this one would be when the episode starts, William and Oliver are going towards the crater formerly known as Lian Yu and are searching for his friends and Samantha. While Oliver tells William about himself, we'll have flashbacks showing who survived when the island exploded. We will slowly find out, and that will keep the audience on their toes.
2. What else happened there?
Another possibility is that other things involving the cast happened on that Island. Maybe our season antagonist was on that Island, but Oliver never met him/her. We could see what happened to the characters when they were held by Prometheus, maybe something shocking was revealed to the cast about Oliver. Another possibility is Kovar might be alive.
3. An event we have not seen in Oliver's journey.
We might continue seeing flashbacks to Oliver on the Island. This one being out of order in his journey. Could be the time he first came onto Lian Yu since we sort of skipped the boat making it there. It could be him looking back on it with those fishermen. There is something they can still tell.
Now these are my theories on the flashbacks that the show can do for the first episode that are on the Island. Guggie sort of limited my theories to that spot. Now i want to hear what theories do you have on the flashbacks for Season six's first episode. (Please not Felicity burning in slo mo)