I know that though generally slaves were exploited for manual labor, some with advanced skills were exploited as artisans or house slaves. Did slaveholders purposefully invest in training slaves for a role or did they more just choose slaves that already had the ability to perform the job? Did they ever have a “job opening” and train up a field slave who had no previous experience?
Bonus question: It’s no secret that many slaveholders saw blacks as nothing more than draft animals and were ideologically opposed to a slave learning how to read. Austin Steward, author of “22 Years A Slave” was severely beaten when it was discovered he was teaching himself. Was this a universal view in the South, particularly in regards to slave owners? Or did some see it as another potential way to profit?
If a slaveowner saw potential in a boy or young man, it wasn't uncommon for him to be educated and taught a trade or craft.
The easiest, and most cost-effective way for an enslaver to acquire a slave who was a skilled craftsman was to purchase one. These skilled men were among the most expensive categories of slave one could purchase, but it was a less significant investment than paying for the years of training needed to allow someone to become a master of his craft.
Anecdotally, I've found evidence of a dozen or so apprenticeships like this in Freedmen's Bureau records (out of several hundred children in three Alabama counties).
It was very common for slaves with rudimentary, or even intermediate levels, of training to be rented out for short/medium-term construction projects en masse. Slaves who were truly skilled craftsmen were uncommon, but not incredibly rare.
An exceptional example of this third type is Horace King. Most enslaved artisans never reached anywhere near the degree of prominence King did, but he's the case I'm most familiar with.
Horace King was born in South Carolina in 1807, and was trained as an architect and bridge builder in his adolescence. He moved to Alabama (still enslaved) in the 1830s. He completed dozens of construction projects with his enslaver, John Godwin. They entered into a highly unusual sort of partnership, with King acknowledged as the co-builder of their projects. An enslaved artisan being publicly credited for his work was highly unusual. I've only ever seen their names recorded in plantation records, for accounting/billing purposes, though I know of a handful of others who achieved some public fame.
In 1846, King purchased his freedom. However, Alabama (like other slave states) did not want freed slaves living in the state. This is due to the restrictive slave codes put in place after Nat Turner's 1831 rebellion, though it was very selectively enforced. To prevent any trouble, King received special permission from the state legislature to remain in Alabama. He bought land (and slaves) and settled near his former owner and they remained business partners until Godwin's death in the 1850s. By this point, King was one of the most famous bridge builders in the Deep South. (He also built parts of the Alabama capitol building, including its beautiful cantilevered spiral staircase!)
King opposed secession, though was drafted. I believe his service was in designing fortifications. After the war, his business continued to thrive, and he served two terms in the state legislature (1868-72). He moved to Georgia, continued to build bridges, and died in 1885.
Two articles you might find useful:
Berry, Daina. “In Pressing Need of Cash: Gender, Skill, and Family Persistence in the Domestic Slave Trade.” The Journal of African American History 92, no. 1 (2007): 22-36.
Kimball, Gregg D. “African-Virginians and the Vernacular Building Tradition in Richmond City, 1790-1860,” in Perspectives in Vernacular Architecture Vol. 4 (1991), 121-129.