We know the following about the pokemon region geography.

>Johto is next to Kanto
>Sinnoh is north of Johto
(Sinjoh being between them)
>Kanto, Johto and at least Sinnoh is part of one island
>Sevii is south of Kanto
>Kalos is relatively close to Hoenn
(two different people mentioning it in pic related)
>Unova is relatively far from the other regions
>Alola is relatively far from the other regions (though I assume closer than Unova based on all the Kanto/Johto/Kalos influences

Also, outside of the Sevii sidequest, do we have any in game references to Hoenn being near Kanto? Or do we just assume it is based on the real world map? Because network communications doesnt really mean they have to be close (though I also think they are)