Start by lining your 9x9-inch baking pan with parchment paper. Leave some overhang on the sides to make it easier to lift the bars out later.
If you’re using a food processor, add the pitted dates and pulse until they form a sticky paste. If you don’t have a food processor, finely chop the dates and then mix them with the other ingredients.
In a large mixing bowl, combine the crisp rice cereal, quick-cooking oats, coarsely chopped peanuts, ground flaxseed, ground cinnamon, and a pinch of salt. Stir well to combine.
In a separate bowl, mix together the peanut butter, brown rice syrup, and vanilla extract until smooth. If your peanut butter is too thick, you can warm it slightly in the microwave to make mixing easier.
Pour the peanut butter mixture into the dry ingredients and mix with a spatula until everything is well combined. If you’re adding chocolate chips, fold them in at this stage.
Using your spatula, transfer the mixture into the prepared baking pan. Press it down firmly and evenly. This step is crucial for ensuring that your bars hold their shape.
Place the pan in the refrigerator for at least 30 minutes to allow the mixture to firm up. This will make cutting them into bars much easier.
Once chilled, lift the mixture out of the pan using the parchment paper overhang. Cut into bars of your desired size. Enjoy your Homemade Clif Bars (No-Bake!) right away, or store them for later!