How did the west african slave traders usually obtain the slaves they sold to europeans?

In those times, tribes in West Africa are very vulnerable. They lived in villages with little to no defense at all. The citizens just litter the place and they can easily be abducted. All that the West African slavers got to do is to burn the huts where the poor citizens hide so they can lure them out and then capture them using crude nets often dressed with sharp metal hooks to stop resistance.