Lightly coat a 9 x 9 baking pan with non-stick cooking spray. Set it aside for now.
Add a 12-ounce package of mini marshmallows to a large microwave-safe bowl and top with the squares of butter. Microwave for 1 ½ minutes. Then, stir with a rubber spatula until it's a smooth buttery marshmallow mixture. Make sure to fully incorporate the melted butter into the marshmallows.
Then, add the vanilla extract, salt and green food coloring to the melted marshmallows. Start with 1 teaspoon of green color and add more as desired. Stir again until the gooey marshmallow mixture is a uniform shade of green. Make sure to scrape the bottom and sides of the bowl!
Stir in the rice krispies cereal making sure that all the cereal is fully coated with the green marshmallow mixture. Then, use your spatula to scoop the rice krispies into the prepared pan.
Lightly wet your hands and gently press the rice krispies into the pan, making the top layer even as possible. Don't press too hard because you want the rice krispies treats to stay soft and gooey! Let the Frankenstein rice krispies treats sit in the pan for about one to two hours to cool and firm up.
When you're ready to decorate, slice the rice kripsies into equal squares.
Add the chopped almond bark to a small bowl and melt for one minute in the microwave. Stir, microwave for another 30 seconds, and then finally stir until it's smooth.
Lay down a piece of parchment paper or wax paper to set the rice kripsies on after dipping them in the chocolate. To make Frankenstein's hair: dip the top ½-3/4 inch of each rice krispie into the melted chocolate, letting the excess chocolate fully drip off before setting it down. Let the chocolate harden.
Dab the back of each candy eye with a small dot of icing to secure them to Frankenstein's face. Use the icing to draw on a smile below them, and a scar going diagonally across his forehead. Then, use the icing to glue two mini marshmallows, one on the bottom of each side of the treat, to create the bolt in his neck.