How to Make It
Bring a large pot of salted water to a boil. Add green beans; cook until bright green and crisp-tender, about 3 minutes. Drain beans and rinse under cold water until chilled; pat dry with a paper towel.
Melt coconut oil in a large cast-iron skillet over medium-high. Add coconut slices, and cook until browned on one side, about 4 minutes. Stir to loosen coconut; add garlic, mustard seeds, and peppercorns. Cook, stirring often, until mustard seeds pop, about 30 seconds. Stir in onion and chiles. Cook, stirring often, until onion and coconut are golden around edges, 3 to 4 minutes.
Add green beans to skillet, and fold to coat. Cook until green beans are heated through, about 3 minutes. Transfer to a platter, and top with coriander seeds and flaky sea salt.