Actually a better answer would have been field hand, house servant, cook ...or in the case of some slave men, they were trained as blackmiths and carpenters.
Of course they were all slaves.
No they weren't "all slaves". Manumission was a fairly common practice in Deep South states, and in the Southern ports, there did exist a rather prosperous free black class, and many of them would go on to form volunteer units for the Confederate Army, granted the lions share of these units originate from Louisiana.
A better answer? Ya mean one that would have appeased more people.
Excellent point, "slave" was a status, not an occupation. Slaves filled many occupations.
Take care of that bad case of Battered Conservative Syndrome you seem to have.