There is plenty of room for variation here, so let your mind and tastebuds run wild. I have a few variation ideas to get you started. And yes, you can definitely double this recipe and press into a 13×9-inch pan insteads of an 8-inch pan.
1 and ¼ cups crisp rice cereal (e.g., I like Erwhon Crisp Brown, but Rice Krispies are fine)
1 cup uncooked quick-cooking oats
2 tablespoons ground flaxseed (flaxseed meal)1/4 cup finely chopped dried fruit (e.g., raisins, dried cranberries, dried cherries, etc.)
¼ cup finely chopped nuts or seeds (pepitas are great)
⅓ cup honey, maple syrup or brown rice syrup
½ cup nut or seed butter of your choice (e.g., peanut butter, almond butter, sunflower seed butter)
1 teaspoon vanilla extract
Optional: ½ teaspoon ground cinnamon
Combine the rice cereal, oats, flaxseed meal, dried fruit, and nuts in a large bowl.
Combine the syrup and nut butter in a small saucepan over medium heat, stirring until melted and well-blended (alternatively microwave in small microwave-safe bowl 30-60 seconds until melted). Stir in vanilla until blended.
Pour nut butter mixture over cereal mixture, stirring until coated (use a wooden spoon at first, then get your hands in it. It will be sticky, but this way you can really coat everything. Just scrape off your hands when you’re done).
Press mixture firmly into an 8-inch square pan (sprayed with nonstick cooking spray) using a large square of wax paper (really tamp it down).
Cool in pan on a wire rack, then chill at least 30 minutes to help it set.
Cut into 12 bars. (Wrap bars tightly in plastic wrap and store in the refrigerator).