Cook Rice: Rinse black rice, then cook in 2 cups water with a pinch of salt for 30-35 minutes. Let cool.
Make Dressing: Whisk lime juice, fish sauce, honey, garlic, and chili flakes in a bowl.
Toast Coconut: In a dry skillet, toast coconut until golden (2-3 mins).
Assemble: In a large bowl, combine rice, mango, bell pepper, cucumber, mint, and cilantro. Toss with dressing.
Garnish: Top with toasted coconut and peanuts before serving.