The exact nature of your question is a bit confusing. I understand it as how one can link the experiences of slavery and the Witchcraft accusation narrative. When I read it, the first figure to enter my mind would be Tituba. I think that it is not mistakable to see her as one bridge between both. She is mostly a forgotten figure in the Salem Witchcraft story, but I think that she holds a great deal of importance. In both the slave predicament and the Witchcraft accusation narrative, one sees the fear of "the other." This demonizing of those who are different leads to social repression and outward subjugation from a political order in order to control the elements that are different. Tituba is a slave, and automatically is seen as an element that needs to be subjugated, controlled, and is "demonized" as being different. Her exact ancestry is something of a question, but I think that the argument can be made that many in America at the time viewed slaves, and people of color, in this demonizing light. This has much of connection with the Witchcraft accusations, where if one were perceived to be a "witch," there was immediate demonizing and intense subjugation.
Tituba takes the worst of both worlds, and there could be a real interesting debate as to which one holds greater sway in her predicament. The question would be whether or not she is a witch. Certainly, there has been literature to suggest as much. Yet, I also think that part of this has to be seen in the light of Salem, or Colonial America, at the time. If one worshipped religion or spirituality differently, they were automatically deemed "a witch." There was little middle ground here. Tituba might have been a witch, but she also might have worshipped divinity in a different light. Given her background of Caribbean roots and the cultural expressions of provident worship, it could very well be that she was seen to be a "witch" because her form of worship was so different than Puritan times. The other half of this could be that she was an easy target for Abigail and the girls because she was a slave. It seems very unlikely that the word of a slave would be taken over two "upstanding" Puritan lasses. In this light, there is a convergence between being a slave or seen as "different" and the propensity to apply the label of being a witch as a result of it. In this setting, the complexity of religious worship and slave narrative is put aside in place of fear of "the other" dominating all else. When Tituba speaks of the devil being present in Salem, she might be articulating a complex religious belief that argues good and evil are multidimensional elements present in all aspects of daily life. Yet, in the simplistic and reductive social and political orders that seemed predicated on demonizing "the other," such complexity becomes one of the first victims to subjugation. In examining the question posed, I think that Tituba would have to be seen as a character that requires analysis and study.