I hope you notice I didn't mention chattel slavery. Even prior to it, all forms of slavery were about removing the agency of person and subjugating the will of the slave to the owner. That requires an active action. Not hiring someone is a passive action. As said by many, you are not entitled to a wage. In fact, suggesting otherwise would actually require slavery. Wage slavery, instead, is a description of a particular material condition of destitution, not necessarily connected to the ethical evaluation to proper slavery. No one says "wage slavery is freedom". What the "universal liberal world", that is, the pro-free market side says is that people should be free to associate with each other as they see fit. Being hired to provide labor in exchange for wage, the basis for wage work, is merely an extension of this. While wage work is a requirement for wage slavery, at no point economic liberals said that everyone should live under wage slavery conditions.