01 - Line a rimmed baking sheet with parchment paper and set aside.
02 - Heat a dry skillet over medium heat. Add the coconut flakes and toast for 2 to 3 minutes, stirring frequently, until golden brown and fragrant. Remove from the skillet and set aside.
03 - Place the chopped dark chocolate in a heatproof bowl set over a pot of gently simmering water (double boiler method). Stir continuously until the chocolate is completely smooth and melted. Alternatively, microwave in 30-second bursts, stirring between each interval, until fully melted.
04 - Remove the melted chocolate from heat. Fold in half of the chopped walnuts, half of the toasted coconut flakes, and all of the pumpkin seeds if using, stirring gently to distribute evenly.
05 - Pour the chocolate mixture onto the prepared baking sheet. Using an offset spatula, spread it evenly to approximately ¼-inch thickness.
06 - Scatter the remaining walnuts and toasted coconut flakes evenly over the surface. Finish with a light sprinkle of flaky sea salt.
07 - Transfer the baking sheet to the refrigerator and chill for 30 to 40 minutes, or until the bark is completely firm and set.
08 - Remove from the refrigerator. Break the bark into irregular bite-sized pieces by hand or with a sharp knife. Store in an airtight container in a cool, dry place.