Line a 9×13-inch baking pan with parchment paper. Lightly grease the parchment with nonstick spray. Set aside.

In a large pot over medium heat, melt the butter. Add the marshmallows and stir until the marshmallows are melted.

Remove pot from the heat and immediately stir in the vanilla extract and salt. Fold in the crispy rice cereal. Make sure the cereal is well coated with the marshmallow mixture.

Transfer mixture to prepared pan and spread mixture into an even layer. Use a lightly greased rubber spatula to help spread and press the mixture down into the pan (don’t pack it down too hard). You can also use a layer of wax paper or parchment paper on top and press down using your hands.

Let treats set for at least 1 hour at room temperature.

Use the edges of the parchment paper to lift the entire rice krispie treats out of the pan. Cut into squares and serve.