Capitalism precisely precludes slavery. One of the most important and foundational of its principles is private property. The first, most natural, and universal instance of private property is the ownership of one's own body. Heck, we even have the phrase "private parts." Slavery requires the most basic violation of bodily autonomy. In other words, to permit slavery is to permit the violation of the most basic property right. I struggle to see how slavery could be compatible with capitalism.
Go ask kids forced to work for years in cocoa plants or coltan mins in africa what they think of your little explaination