Slave Taker? Last step - Assign a Crafting Thrall to a station?
Pretty obvious.
You assign a crafter to a crafting station, be it a blacksmith bench or carpenter bench or so.
You gotta try this multiple times with different Tiers of crafters and different types and Tiers of stations.
Try drag the crafter directly into the “personel” slot of the stations, or the inventory slot, then the personel slot.
And last but not least, pray to Crom for the miracle to happen.