I was recently shopping for some new mixed media elements. I was ready to recycle the plastic form trays that they come in when I realized they were an exact mold of the original.
I found another to make keys. I started thinking even more outside the box and found a plastic mold off of my cupcake papers that will work too!
I would suggest that you lightly spray the mold with cooking spray before adding your paperclay. Let the clay dry partially before removing it from the mold.
I was really excited to share this tip with you. I am now looking at everything I purchase to see if I can use it as a mold. I love the fact that I not only have great molds but I reused something that would have normally been tossed or recycled.
I would love to hear what interesting items you have used to make a mold.