I wanted to create the jewelry that was in my head and this is how I accomplished that. (24 hrs because that's when everything is done drying)
Make a heart shape in your graphic editing program with the dimensions that you want the heart to be and, print it out. You can make more than one at a time and put several of the shapes on an 8x10 piece of paper.
Slowly and carefully cut the hearts out.
Roll some white polymer clay out on a glass (glass works better with clay) baking pan so that it is about 4 or 5 mm thick. Gently lay the heart shape down on the clay and cut around the edge with a sharp utility knife. Cut about 2 mm from the edge of the shape. Remove the excess clay from around the shape.
Preheat a conventional oven at the temperature specified on the directions for your polymer clay and, bake your shapes for the time specified in the directions.
Remove the pan from the oven and wait for the shapes to cool completely. Now you can gently file the edges with a fine grit sandpaper to make them nice and smooth and even.
Brush some of the decoupage varnish on the back of the shape and smooth it onto the clay shape. Make sure it is centered. Wait for it to dry and brush on one or two coats of the decoupage. When those coats are dry, you can then spray on some acrylic gloss to protect it even further.
Use E6000 glue to attach the shape to a ring base and allow the glue to dry for at least 24 hours before wearing your beautiful new ring.