Sarah posted a comment asking what I used to adhere the broken porcelain plate bits to the clay pot. For this project, I used a mastic adhesive that comes in a little tub, ready to go.
It takes only a small amount to adhere each piece, and it doesn't dry so quickly that you can't adjust it a bit if it isn't exactly where you want it. You can get mastic at Lowe's or Home Depot or a local hardware store. Be sure to tightly reseal the tub after use so it doesn't dry out.