In a spacious mixing bowl, blend together the rolled oats, peanut butter, maple syrup, melted coconut oil, and vanilla extract. Mix well until everything is fully combined and the mixture holds together when pressed.

Line an 8x8-inch baking dish with parchment paper. Transfer the base mixture into the dish and spread it out evenly with a spatula or your hands. Press it down firmly to form a solid, compact layer. Place the dish in the refrigerator to chill while you prepare the chocolate topping.

In a heatproof bowl, melt the vegan chocolate and coconut oil over a double boiler or in the microwave (in 30-second intervals, stirring in between) until smooth and fully melted.

Remove the baking dish from the refrigerator and pour the melted chocolate over the base layer. Spread it evenly with a spatula. If desired, sprinkle sea salt flakes, chopped nuts, or shredded coconut on top for added texture and flavor.

Return the dish to the refrigerator and let it chill for at least 1 hour, or until the chocolate is completely set. Once firm, lift the parchment paper out of the dish and place it on a cutting board.

With a sharp knife, cut the chilled mixture into 12 even bars. Serve immediately or store for later.