Coat a 9- by 13-inch rimmed baking sheet with coconut oil and line with parchment. Melt 16 ounces 70% dark chocolate, 1/3 cup almond butter, and 1/8 teaspoon fine sea salt in a heatproof bowl set over simmering water, stirring until smooth. Pour melted chocolate over parchment and spread in an even layer. Sprinkle with ¼ cup unsweetened shredded coconut. Refrigerate until firm and then break into pieces.