Whisk the coconut milk, mango juice, minced ginger, green curry paste, and a pinch of sea salt together in the bottom of a 7-quart slow cooker until smooth.
Stir in the sliced carrots, then add the chicken breasts or thighs, spooning the sauce over the top to coat.
Cover and cook on low until the chicken is tender and cooked through, about 5 to 6 hours.
When the chicken is done, remove it to a plate and cover to keep warm.
In a small bowl, whisk 4 teaspoons tapioca starch with 8 teaspoons of sauce taken from the slow cooker until smooth.
Stir the tapioca slurry back into the slow cooker, then add the broccoli florets and cubed red bell peppers. Cover and set the slow cooker to high; cook until the sauce thickens and the vegetables are tender, about 1 to 1½ hours.
While the sauce thickens, pulse the cauliflower florets in a food processor until they resemble rice.
Heat the coconut oil in a large skillet over medium-high heat. Add the cauliflower rice and coconut flakes and cook until lightly golden, about 2–3 minutes, then cover, reduce heat to medium, and cook until tender, about 2–4 minutes more; remove from heat and set aside.
Shred the cooked chicken with two forks and stir it back into the thickened sauce in the slow cooker.
Divide the cauliflower rice among 4 bowls, top with the mango-chicken curry, scatter the cubed mango on top, and garnish with cilantro and sliced green onion.
