Historically speaking, in a lot of societies a slave had little to no rights. You were another person's property, in the worst case you had as much rights as a table, and everyone saw that as completely normal.
I'll talk a bit about the Romans. The position of a slave varied a whole lot between different cultures, eras, and states, but I picked Rome because that's where I'm best versed in.
So. If you were one of the lucky few, you could have a fairly good position, like a teacher or a secretary, if you were an educated man. In the worst case you could be mining in unspeakably horrid working conditions, and die very early from disease/malnutrition/injury/abuse or whatever.
Still, no matter what work you did, you were completely vulnerable to your master's whims. He could kill you with no consequences. (IIRC later someone, maybe Claudius, made it illegal to kill a slave for no good reason. One can only ask what they considered a good reason.) You could get whipped. In addition to not getting to choose where you worked, you couldn't choose where you lived either. You couldn't get married. You couldn't own property because you were property yourself.
So, even if you now got forced to work X job, you'd still have so many rights. Your boss can't chain you to your table or whatever and beat the living shit out of you if they feel like it. (yet)
I remember when once I ate a ton of red bell peppers and got jumpscared when my shit was red. I think the color was like this: