They don't, this is a lie from the country that's been embargoing Cuba into oblivion for sixty years.

It's not a lie. It's well-documented, and happens outside of the bubble in which Cuba can keep its slavery quiet.

"Host" nations agree to pay Cuba for the doctor's work, agree not to pay the doctor directly, and agree to deport them back to Cuba if they attempt to negotiate being paid directly. This is slavery by anyone's definition.

Sounds like agency work with a visa thrown in. The doctor is ultimately paid by cuba, no?

The slave is ultimately fed by the slaveowner, eh?