One-Pot Lemongrass Chicken with Rice

Ingredients

1/4 cup lemongrass (white parts only, dark green parts reserved for trussing) (about 2 stalks)
3 tablespoons fish sauce
3 tablespoons light brown sugar
3 tablespoons unrefined coconut oil, divided
4 garlic cloves, peeled and smashed
1/2 teaspoon black pepper
1 (4-pound) chicken, patted dry, excess skin around neck and cavity trimmed
1 teaspoon kosher salt, divided
1 1/2 cups plus 1/3 cup coconut water, divided
1 1/4 cups uncooked jasmine rice
1/3 cup unsweetened toasted coconut flakes, plus more for garnish
Thinly sliced scallions and sliced red Fresno chiles, for garnish