1) The standardization of the product (nothing hand-made: everything is made through machines, molds and not by skilled craftsmanship)
2) The use of special-purpose tools and/or equipment designed to make assembly lines possible: tools are designed to permit workers with low skill levels to operate "assembly lines" - where each worker does one task over and over and over again - like on a doll assembly line, where one worker might spend all day every day screwing on doll heads.
3) Workers are paid higher "living" wages, so they can afford to purchase the products they make.