It's really key for people to understand this, because that economic imbalance doesn't require slaves, though slaves are a sufficient condition.

It can also be done (on paper at least) with automation. The key point is "capital consolidation (which can scale) divorced from individual labor output (which does not scale)," and however you get there (slaves or robots), you can create a massive societal wealth imbalance that results in an economic arrangement utterly unlike the arrangement that spawned it.

... that reminds me, my phone pinged five minutes ago. I should go pick up that Amazon package off my porch.