Virtually everyone is forced to work, or face death. Being forced to work is the de facto human experience. Effectively, there isn't a choice to work or not.

Presenting work as a choice is closely analagous to presenting eating as a choice

Pay, or relative lack thereof, is what defines degree of slavery (complete or partial).

The only real arguments being a.) if one is paid what the work is worth and b.) how much of that pay is retaken in the form of taxes (direct or indirect like when company towns, or estates, recoup most of the pay in the form of costs to the laborer).

Therefore, we will add an additional form of enslavement process: purposefully (often illegally) diulting the value of labor so that it is cheaper.

If a serf is "paid" but the boss and landlord recoups nearly all of that pay in rent and taxes, is the serf a slave?

Few moral and logical people would say no.

Slaver hand-waving deserves to be called out.