Cut the fish into large 2-inch chunks, pat dry and place in a bowl. Season with salt, lime zest from one lime and 1 tablespoon lime juice, and massage lightly to coat. Set aside.
In an extra-large saute pan, heat the coconut oil over medium heat. Add the shallots and saute until golden, about 4 minutes. Add the garlic, lemongrass and fresh chilies. Saute 3-4 more minutes, until fragrant. Turn heat to low. Grate the ginger and turmeric and add the Thai Curry paste if using, saute 1 minute. Add the chicken stock, kaffir lime leaves , salt, carrots and bell pepper. Cover, bring to a simmer and simmer gently for 5 minutes until the carrots are tender.
Once tender, stir in the coconut milk and fish sauce, and a generous squeeze of lime juice- start with half a lime, add more to taste.
Taste it- coconut broth should be salty, lime-y and a little spicy- and adjust to your taste. Add more fish sauce, Thai Curry paste, garlic chili paste, be bold here -keeping in mind all the flavors will mellow out with the addition of the fish, veggies and with it being served over rice.
Nestle in the fish, and quick cooking veggies. Simmer gently over medium low heat, spooning the coconut broth over the top, or turning the fish over after the bottom half is cooked and becomes opaque, about 3 -4 minutes. You can also place this in a warm 350F oven to fish cooking.
Garnish with basil or Thai basil, or cilantro and lime wedges.
Serve over rice or cauliflower rice.