Through the reference below, which defines the term, I found the French "travail à façon", which Harrap gives as "job work".

An alternative could be 'someone working under a job work arrangement'. See the reference below for a definition of the term.

I think the phrase you're looking for is pieceworker. The dikke Van Dale gives 'maakloon' as 'loon voor het maken van iets, m.n. voor het maken van kledingstukken.' (See below)

A pieceworker is an employee who is usually paid on the basis of results, eg paid
on a rate per article produced, such as a shearer or sewing machinist. ...