Do the areas swap or are they the same like Underswap?
Well I don't know. In Underswap areas don't swap at all so they would likely be the same in Flipflopped but alot of things would be different due to the swaps, like new Puzzles in Snowdin, The Ruins being more Fabulous with pretty light and lanterns everywhere with the Ruins being darker I think, etc.
But some interations of Underswap use the old TS! Underswap areas.
Like Ruined Home, Sunnedout, Crystal Springs, and Coldsea (Which is so damn catchy by the way).
But I think for Flipflopped I might reuse the areas from my failure Underswap take, Pigster's Underswap, where it goes for the same theme but new seasons. For those who aren't aware of Pigster's Underswap and the areas. They go like this.
Ruins (Fall) -> The Catacombs or Hapstablook's Amusement Park of Wows and Wonders (Summer) (Yes Hapstablook turned the Ruins into an amusement park, I am not kidding.)
Snowdin (Winter) -> Fallout Woods and Fallout Town(Fall. Duh.)
Waterfall (Spring) -> Dry Ice Express (Winter) which was basically Ice Cap from Sonic 3 and TS! Underswap's old Coldsea but it's in an Ice Cave but it also had a high speed moving train section where Chara would fight Alphys on top of the Train.
Hotland (Summer) -> Pollen Plain + Spooky Sprint (Spring) which was like the Mushroom Areas from Kirby's Epic Yarn and Mushroom Hill Zone from Sonic & Knuckles. And Spooky Sprint was basically this tag team race thing that was Pacifist Route only where Chara would team up with Papyrus and go through a spooky mansion that turned Undertale in a Horror game.
So basically those were the areas in Pigster's Underswap but that was a failed Underswap take so I guys I could probably reuse them for Flipflopped but that's only if Underswap used the old TS! Underswap Areas. They would be pretty interesting if they were used here, but of course I would have to change some things to fit Flipflopped like Spooky Sprint not existing since "Napstabolt" isn't a thing here and Fallout Woods and Pollen Plains would be changed to be less generic looking.
I'd be down to bring them back if people wanted them to, but for now, I think altered versions of Undertale's areas is what we should go for, atleast for right now. :)