Line a 9 x 6 x 2-inch baking dish, or something similar, with parchment paper and set aside.
In a large mixing bowl, toss together puffed brown rice, almonds, sunflower seeds, pumpkin seeds, hemp seeds and cinnamon.
In a smaller bowl, whisk together the cashew butter, honey, and melted coconut oil.
Pour the wet ingredients over the dry ingredients and use a silicone spatula to combine thoroughly.
Transfer the mixture to the prepared baking dish, and press it firmly and evenly into the dish.
Add the chocolate to a microwave safe bowl and microwave for 30 seconds at a time, stirring between intervals, until the chocolate is melted.
Drizzle the chocolate over the bars and transfer the baking dish to the fridge to chill for 30 minutes.
Sprinkle flaky salt over the chocolate, and return the dish to the fridge, chilling the bars until the chocolate is fully hardened, about 30 more minutes.
Use a large, sharp knife to slice the bars into roughly 4 x 1-inch pieces. Store in an airtight container in the fridge for up to two weeks, or in the freezer for up to three months.