You will need:
-Clear glycerin soap
First, get the mold ready. The only way I could get the soap to stay in the cookie cutter was to roll out some play-doh, put plastic wrap over it, and then press the cookie cutter down to create a seal around the bottom. This actually worked quite well, but if you don't have a perfect seal around the bottom, the soap runs everywhere. Do not despair, once it's cool enough to touch, you can peel it up, melt it, and try again. :) I also did this on a cookie sheet to spare myself the trouble of cleaning up the counter afterwards.
Next, grab your soap. I used either 3 or 4 cubes, depending on the size of the cookie cutter. Melt in the microwave for 30-40 seconds. Then, add 5-10 drops of food coloring. If you want really vibrant colors, go for 10. You could likely add a couple drops of fragrance at this point, but we tend to be a fragrance-free household.
Stir the food coloring in, and then very carefully pour the hot soap into the mold. I found it helpful to hold down the cookie cutter with one hand while I poured to keep it from leaking out the bottom. Then let it sit for about 30 minutes, until it's cooled, and there you have it!
These turned out really well and the Eskimo loves them. Definitely going to have to do something like this for a birthday gift for someone in the future.