The Sandy Forest is like another game within the game. It follows the same rules and gameplay, has its own map and Helper, and uses the same scarce Resources and Special Items you are struggling so desperately to manage back in the main game.
It becomes available before the Snowy Hills, but is a newer addition to the game and so has not been thoroughly detailed here yet. Feel free to change that. ;-)
It is accessed via the Island Vacation Portal that you find in the Dark Forest at Phase 3 of the Animals Wanna Have Fun quest. Its primary purpose appears to be to help you to run out of Axes as fast as possible. But the maddening part is that it compounds the Bottlenecks of Honey, Quarry Stone and Planks by requiring copious quantities of these Special Items without providing any new means of generating them.
See also: Sandy Forest Quests