The Slave Ship
art by George Roussos, story by Al Feldstein
Weird Fantasy #8 (1951)
Roussos only did a handful of early New Trend stories for the various Feldstein books. I'm mostly familiar with him as an inker of somewhat variable quality over some Kirby and Ditko work in the 1960s for Marvel, and later as one of the main colourists for Marvel. He had quite a long career otherwise, of course, and the EC stories of his I've seen are pretty nice.
This story has a slave ship in 1839 picking up a cargo of slaves from Africa and dumping them in the ocean when they're about to be confronted by a Coast Guard ship. Later their ship is found abandoned, and we flash back to see how they encountered an alien space ship and were taken aboard. As the alien ship was stopped by another ship, the captain realized that they had been taken as slaves, and were about to be let out in space as their captors encountered the space equivalent of the Coast Guard.
You could kind of see the ending coming a mile away, but otherwise it's a nice story with a strong moral lesson that slavery is wrong because someday you might be taken as a slave by aliens. It also teaches us that bodies explode when let out into the vacuum of space, which I'm not sure is true, but there you go.