Shape the slab. Use your needle tool to score (make deep scratches) the angled edges. Again you are creating more surface area for attachment. I use a needle tool instead of a serrated rib because I think it works better to make deeper marks in the clay.
Put slip on both edges and press the edges together. Use the modeling tool to compress the attached edge on the outside and inside of the pot. You can use the sharp end to clean up any extra slip.
Here is one that is finished!