Ok, so I believe the Kuma flashback is taking place in God Valley.
In his Chapter 1074 flashback we see a young Kuma crying; Kuma has seemingly ran away from somewhere.
We see 2 silhouettes find Kuma, claiming they will all receive punishment if he isn’t found. I believe these two are slaves that will be punished for Kuma running away. They have a rough appearance and are missing teeth.
In the photo below, Oda wants us to believe these two things are connected which is why one follows the other image directly. Here is the image.
If you look at the hair of the individual on the right in the above photo, you’ll notice their hair is in some kind of bun and they have some kind of collar or rim around their neck. I believe this person is a Celestial Dragon.
If you pay attention to Celestial Dragons, you’ll notice that the vast majority of them all have some kind of variation of a standing bun on the top of their head. It’s practically a trademark Celestial Dragon hairstyle:
The other piece of important information was the Castle Tower in the second photo from Chapter 1074.
If we are supposed to believe that the location in 1074 is just Mary Geoise, then why doesn’t Oda reveal it to us in a way that informs us this location is Mary Geoise? If it were Mary Geoise, then the plot twist here would be that Kuma is a slave, but being a slave isn’t anything new in One Piece. It would make Kuma and Hancock’s backstory fairly identical.
I looked at Mary Geoise and every picture I could find on the Castle located there and nothing perfectly matches the picture in 1074. MAYBE it could be a random house in Mary Geoise, but Oda is showing us a location to tell us where it is. I believe Oda knows the reader will see the hairstyle and believe this is a Celestial Dragon/Mary Geoise flashback.
I do not think this is Mary Geoise. As I said above, I believe this is God Valley.
We were told just 10 chapters ago in 1064 that Kuma’s body is special.
This arc already has one tie in with the Rocks Pirates through Stussy being a clone of a former member. We could explore the disappearance of the Rocks Pirates in this arc.
Lastly, Kuma is 47 years old at the time of Chapter 1074*, and* God valley happened 38 years ago from present day. That would make Kuma around 9 years old when God Valley disappeared. In his flashback, Kuma looks to match this age.
I believe that Kuma is from a special race that lived on God Valley that the Celestial Dragon’s had enslaved. Oda has saved one of the most highly anticipated backstories in the entire series until the final saga.
*Theory by SpiritualScumlord