Line 6 cereal bowls with plastic wrap or wax paper and set aside.
Melt the butter in a large pan over medium heat. Add the marshmallows and stir until completely melted. Remove from the heat and stir in the cereal and salt until well combined.
Divide the mixture among the prepared bowls and use your hands to press evenly into the bottoms and up the sides of the bowls to result in bowl-shaped cereal treats. Freeze, 1 hour, to set. Remove the treats from the bowls and discard the plastic wrap. Serve as a bowl for your favorite ice cream and toppings.
Cereal bowls are best eaten the day they are made, but they can be stored separated by layers of wax paper in the freezer in an airtight container for up to 4 weeks.