Line a large baking sheet with parchment paper and set aside. Preheat your oven to 350°F (175°C).

Spread the raw almonds in a single layer on a separate baking sheet. Toast in the preheated oven for 8-10 minutes, stirring halfway through, until they're fragrant and one shade darker. Let cool for 5 minutes, then roughly chop half of them, leaving the other half whole.

Place the chopped dark chocolate in a heatproof bowl. Microwave in 30-second intervals, stirring thoroughly between each burst, until the chocolate is melted and smooth with just a few small pieces remaining. Stir until completely smooth.

Pour the melted chocolate onto the prepared parchment-lined baking sheet. Use an offset spatula or the back of a spoon to spread it into an even layer about 1/4-inch thick, roughly 10x12 inches.

Immediately sprinkle the toasted almonds (both whole and chopped) evenly over the chocolate, pressing them gently into the surface so they adhere. Sprinkle with flaky sea salt if using.

Tap the baking sheet firmly on the counter 2-3 times to release any air bubbles and help the almonds settle into the chocolate.

Let the bark set at room temperature for about 2 hours, or until completely firm and the chocolate has lost its sheen. If your kitchen is warm, you can refrigerate for 30 minutes, but return to room temperature before breaking.

Once fully set, break the bark into rustic irregular pieces using your hands or a sharp knife. Store in an airtight container with parchment paper between layers.