Add the maple syrup and coconut oil to a medium saucepan. Bring to a steady boil over medium heat, swirling the pan occasionally. The syrup should bubble evenly and thicken slightly, like a loose caramel that coats the back of a spoon. Boil for about 3 minutes, watching that it does not darken too quickly.

Stir in the sliced almonds and about ½ teaspoon of the flaky salt. Keep stirring until all the almonds look glossy and evenly coated, with no dry spots. Pour the mixture onto a parchment lined baking sheet and spread into a thin layer. Use a fork to separate clumps while the nuts are still hot. Let the almonds cool completely until dry and crisp to the touch, not sticky.

Line a second baking sheet with parchment. Place the chopped dark chocolate in a heatproof bowl set over a small pot of gently simmering water. The bottom of the bowl should not touch the water. Stir until most of the chocolate is melted, then remove from the heat and keep stirring until smooth and shiny. If using a microwave, heat in 10–15 second bursts, stirring between each, until smooth.

Reserve about one third of the candied almonds for the topping. Add the remaining almonds to the melted chocolate and fold gently until they are coated and distributed. The mixture should be thick but spreadable. If it looks very loose, let it sit for a minute so it firms up slightly.

Pour the chocolate and almond mixture onto the prepared parchment lined baking sheet. Use a spatula to spread it into an even layer, about ¼ inch (6 mm) thick. Keep the edges from getting too thin so they do not crumble. Scatter the reserved candied almonds over the top and press them lightly into the surface. Sprinkle the remaining flaky salt evenly over everything.