Place octopus in a large pot, cover with water, and bring to a gentle simmer. Cover and cook 45–60 minutes until fork-tender.
Drain and cool slightly, then cut into large pieces.
Whisk coconut oil, lime juice, garlic, coriander, and chili flakes into a marinade.
Toss octopus pieces in the marinade, cover, and marinate at least 1 hour.
Grill over high heat, turning occasionally, 8–10 minutes until charred at the edges.
Season with salt, top with cilantro, and serve hot with lime wedges.