Line a 9x13-inch baking sheet with parchment paper, letting the edges hang over for easy removal later.
Melt the dark chocolate with the coconut oil in a microwave-safe bowl in 30-second intervals, stirring between each, until completely smooth and glossy.
Pour the melted chocolate onto the prepared baking sheet and spread it into an even layer about 1/4-inch thick using an offset spatula.
Warm the peanut butter in the microwave for 15-20 seconds until it's fluid enough to drizzle easily.
Drop spoonfuls of peanut butter evenly across the chocolate surface, then use a butter knife or skewer to gently swirl it through the chocolate in figure-eight motions.
Sprinkle with sea salt and any additional toppings while the chocolate is still wet.
Refrigerate for 20-30 minutes until completely firm and set.
Lift the bark out using the parchment paper overhang, then break into irregular pieces by hand or cut with a sharp knife.
