I used this Birch wood disk from Hobby Lobby as my base. It's already sanded right out of the store.
Apply a light layer of colored stain. I applied with a foam brush and immediately wiped off. I wanted to be able to still see the wood grain. I used a Weathered Gray color.
Arrange the keys in a pattern of your choosing. I liked the concentric rings. You might like a different look.
Apply a drop or two of superglue to each key. Use a toothpick to spread the glue around. I also wear nitrile gloves to protect my skin. The gel-type glue works best.
Allow the glue to dry over night before you use the trivet.
Begin enjoying your craftily made trivet!