Prepare a 9x13 dish by spraying with oil, then line it with parchment paper. Spray the paper lightly and set the pan aside for later.
Place the butter in a large pot and melt over a medium- low heat. Once melted, bump the heat up to medium and cook, stirring regularly, until the butter begins to turn a light amber.
Remove the pot from the heat and stir in the marshmallows. Once the marshmallows are starting to melt and incorporate into the butter, place the pot back on a medium- low heat. Stir until the mixture is completely melted and combined.
Turn off the heat and stir in the caramel, vanilla, and salt. Once well combined, scrape any excess mixture off of the spatula and spray the spatula with oil. Fold in the puffed rice cereal until completely combined.
Add roughly 1/2 - 2/3 of the mixture to the prepared pan. If desired, lightly drizzle on more caramel sauce. Top with the remaining mixture and use a greased spatula to gently, but firmly, press it into the pan. I like to finish it off by greasing the bottom of a glass and gently pressing the surface to ensure it is well packed and even.
Let the rice krispie treats cool and set up for at least 30 minutes, or overnight. Once firm, slice into squares. If using the candy melts, melt then with the coconut oil in the microwave. Do 10 second bursts at 50% power until you have a smooth consistency (do NOT overheat!). Drizzle over the squares and let it set for 15 minutes. Enjoy!
To store: layer the squares between parchment paper in an airtight container. Keep on the counter for up to a week.