If I don't say anything it does not mean that I am sleeping. I am not retired yet. Just tired.
Unfortunately I don't read Spanish that well and I am definitely not familiar with Spanish SF. I know more about the French one but I don't recall anything about time travel and slavery. I am pretty sure that in both Spanish and French SF slavery is a quite
rare subject, taking into account the history of the two countries.
It may be possible to find something from Haiti (but I don't know much about any literature from there), other islands in the area (Cuba maybe). Another possibility is Brazil.
Gabriel