As you might have noticed, the term "rebozo" can mean several different things. It can be a type of wrap, a type of pass (where the wrap goes over one shoulder and under the opposite shoulder), or a type of carry. In this context, a rebozo carry is very similar to a ring sling, except we are using a slip knot at the corsage level position rather than sling rings.
Slip knots were very confusing to me in the beginning, so please don't give up if this carry does not work for you right away! For me, it took the right wrap (thin!) for it to finally click. It may be the opposite for you. Thin wraps can be easier to work with while learning carries, but they are also easier to overtighten in a slip knot, making them more difficult to adjust. Play around with it and see how you do. I find it can be very comfortable once I find that sweet spot!
Here is a detailed slip knot tutorial: https://www.youtube.com/watch?v=Va30BaXw2a0
Here is a video to help with the whole rebozo carry: https://www.youtube.com/watch?v=PHD7JziOgME