Line a standard baking sheet with parchment paper or a silicone mat.
Place the chopped dark chocolate in a heat-proof bowl and melt using a double boiler method, ensuring the water does not touch the bottom of the bowl, or microwave in 30-second intervals until the internal temperature reaches 115°F (46°C).
Stir the chocolate continuously until smooth and allow to cool slightly to 90°F (32°C) for optimal temper.
Incorporate 3/4 cup of the roasted almonds into the chocolate mass.
Pour the mixture onto the prepared baking sheet and use an offset spatula to spread the chocolate to a uniform thickness of 6mm (approx. 1/4 inch).
Scatter the remaining 1/4 cup of almonds across the surface and immediately apply the flaky sea salt.
Refrigerate the sheet for 30 minutes or until the chocolate has reached a fully crystallized, solid state.
Break the bark into irregular fragments by hand or using a chef's knife for clean edges.