If we're just talking fiction, the Star Wars. Think about it. Droids are clearly a sentient slave race.
Well . . .
Not sure that's actual slavery. Some people portray it as such, but how do we know that Santa doesn't pay them? It's up to the imagination of the person relating the story.
Housewives might count. They don't get paid for their labor. Sure, they are allowed to leave, but for what?
Single motherhood? Kids also provide free labor, but it depends on the attitude whether it is "contributing the household" or "slavery." Parents can use the same argument for the free labor they provide, if they are being very juvenile and obnoxious.
You'll have to define slavery carefully before you explore this problem deeply.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.