Free Trade is NOT a two way street.
A free country, U.S., CANNOT trade freely with a SLAVE State. Otherwise, you also become a slave.
Print your tee shirts in your shop right next to a slave tee shirt shop. What happens to your business? It dies. You die.
Slaves makes poor quality junk. Period.
American slaves excelled at agricultural production.
At every plantation there were skilled carpenters at work producing all sorts of things made from wood. There is evidence that a Maryland slave designed and produced a very special wheel chair for the mistress of the house.
and on an on