Place the 1 cup (120 g) roasted cocoa nibs in a dry skillet and toast over low heat, stirring continuously, until the nibs are warm, fragrant, and shiny, about 3 minutes. Remove from heat immediately to avoid burning.
Transfer the toasted nibs to a blender or mini food processor. Add 2 tablespoons of the coarse-grained granulated sugar, 2 teaspoons of the hazelnut oil, and a pinch of flaky sea salt.
Grind/process the mixture, stopping every 20–30 seconds to scrape down the sides, until it forms a shiny paste. This will take about 1–3 minutes; the paste should be cohesive but still noticeably crunchy, not a smooth puree. If the mixture stays dry and will not come together, add up to 1 additional teaspoon hazelnut oil (for a total of 3 teaspoons) and continue processing until it holds together.
Transfer the paste to a bowl and stir in the remaining 1 1/2 teaspoons granulated sugar by hand until evenly distributed.
Spread the chocolate-hazelnut mixture on warm toast and sprinkle with a few flakes of flaky sea salt to finish.