Line an 8-inch square pan with parchment, leaving overhang, and lightly coat with nonstick spray.
Melt 2 cups chocolate chips with 1 tablespoon coconut oil in short microwave bursts until smooth.
Fold in the crispy rice cereal until coated. Spread into the pan and press firmly into an even layer.
Chill the base for 10 minutes, just until it holds together.
Warm caramels, heavy cream, butter, and fine salt in a saucepan over low heat, stirring until melted and smooth.
Stir in vanilla and let the caramel thicken for 2 minutes off heat.
Pour caramel over the chocolate-cereal layer. Tilt to level and chill until tacky, about 15 minutes.
Melt remaining 1 cup chocolate chips with remaining 1 tablespoon coconut oil. Spread on top and sprinkle flaky salt.
Chill until firm, then use the parchment to lift out and slice into bars with a warm knife.