Just a few concept sketches to how Soul's home will develop into by the time her main story arc comes around. I don't find it a huge spoiler, just there to let you know that her story takes place in the version of the multiverse where each au is shown as a floating island with a door.

Hers doesn't have a door and is just the island because she doesn't have an au. This is NOT and AU. This is an actual landmark where she can rest and wait until her next 'patient' is in need of her help.

If you can't tell, this island is mostly water. There is a small bit of land at the tip but near the wide end, there's a mount of rocks (I say mount because it's not tall enough to be a mountain but also not small enough to be a hill). At the top of the mount, there is a small, never-ending pool of water, which waterfalls into a lagoon sort of area. in the middle is another small patch of land, smaller than the one at the tip.

The actual topography (I suggest you look that up) is that near where there is land, the water is shallow but when moving farther away from land, it dips down deep (much like a bowl). Because of the never-ending flow of water, the 'bowl' is constantly over-flowing into... basically oblivion.

Soul can walk on water so she has no trouble navigating her home but other characters, such as ink, error, dream, and nightmare, attempt to follow her to the middle of the island, they would have to swim. Unfortunately for them, the water is dangerous because it is constantly moving towards the edge through currents from the flow of the water. Again, this has no effect on her. Beautiful, but a death trap for intruders. 

P.S. She will not care if they are about to die. She was made to heal souls not meant to die. If you die and stay dead, she will not care. Mostly because she expects, if you were able to get to her island, which is located at the very far edge of the multiverse, you are more than capable to save yourself. (Unless you are a child... because she loves children... but that's for another day)