1Line an 8x8-inch baking pan with parchment paper, leaving some overhang on the sides.
2In a large bowl, combine oats, rice cereal (if using), chocolate chips, flaxseed, cinnamon, and salt.
3In a small saucepan over low heat, combine peanut butter, honey, and coconut oil. Stir until smooth and melted. Remove from heat and stir in vanilla extract.
4Pour the wet mixture over the dry ingredients and stir until well combined.
5Transfer to the prepared pan and press down firmly and evenly.
6Refrigerate for at least 1 hour, or until set.
7Lift the bars out using the parchment overhang and cut into 8–10 bars.
8Store in an airtight container in the refrigerator for up to 1 week.