Either you don't understand how chattel slavery works or you simply ignore the fact that you don't need any of those prerequisites you're dearly holding unto for something to be property it. Which is it? The ownership of property - all property, including slaves - is transferred with money, contracts and the legal recognition of both. The ownership is maintained through force. Why is this so hard for you to comprehend?The control and ownership of a piece of dirt and rocks, a car, a couch, a plane or some other inanimate object can easily be shown to be transferable. I can't control people because I can't truly assume control over them. It can never truly be a transferable object to the fullest extent of the word.
There are things that are simply not transferable, and other things that are not able to be owned at all, like for example, an idea.