Prepare an 8x8 pan generously with butter or parchment. Set to the side.
Place the Lucky Charms cereal in a large bowl and set to the side.
In a medium-sized saucepan, melt the butter.
Right as the butter is melted, add in the marshmallows and the salt. Mix continuously until the butter and marshmallows have formed into one cohesive mixture. Remove from the heat.
Pour the marshmallow mixture on top of the Lucky Charms cereal. Use a rubber spatula to cover the cereal in the marshmallow mixture.
Press the cereal mixture into the prepared pan using the rubber spatula. Press down with the spatula or a piece of parchment paper to get a smooth top.
Let the Rice Krispie treats set in the pan for 30 minutes. If you want to speed up the process, place the treats in the refrigerator. Use a sharp knife to cut them into squares.
