Yeah that's a great point Light! I think you can do slice of life on pretty much any site. I wonder what's the distinct difference between a site labelled slice of life oppose to one that isn't. Is it the events that pose some threats to people that makes it different or something else? You really brought up a great point!
I've personally always viewed this as being a matter of intention & focus
A site with a major over arching plot and factions intends to be a plot driven action including story with events and plot influence and things determined by character interactions etc etc.it's more like a story book or an action movie and the intent from the beginning is to pass through Plot check points and play out the story as participants in it.
Slice of life is more about a setting and general interactions resulting in something far more laid back. The goal is to have a nice general setting for characters to established in but no over arching canon story, it's more about the blending of every day adventures and shenanigans with the occasional "but what if this happened?!?" Thrown in to help keep it spicy. They also tend to rely more heavily on member driven plots to make stuff happen than staff driven.
Ex:
A fantasy site where vampires and werewolves hate each other and have been warring for centuries, the war is hitting a boiling point and about to bleed into human society upsetting the cosmic balance between the special and the not, how will you survive when the world starts to fall apart?!?!
Vs
A fantasy site where non humans coexist with humanity, magic and gods are abundant and well received. Peace is the common state of mind and the world can't wait to hear your story.
The latter is most likely to be labeled slice of life because while a werewolf pack and a vamp coven might be fighting in it the intention of the site is not to focus on them specifically, just to let them exist.
A fantasy site where they are the focus may have slice of life elements or characters in it but they are not its main focus, just something that isn't entirely shunned because there's no reason for it to be pushed out when it's just kinda there.
Eta: to be a good girl and obey the rules of the thread..... Kinda feeling a semi modern fantasy setting again. Just a little bit. Miss playing my unruly demons/vamps