A variety of custom word stamps. I stamped the "Thankful" stamp into some black polymer clay using Pearl Ex powders as a release (& to help it show up in the photo). You could also use a water release, then use acrylic paints in the impressed areas after baking to make the message stand out more.
Read more in this blog post: Stamp Your Own Message in Polymer Clay
Inspired by: Kathy Canuel's PCC Tutorial on making custom word stamps with polymer clay.