How to Make It
Combine onions, carrots, vinegar, garlic, ginger, chile, lime juice, allspice, and salt in a large bowl; toss to combine. Cover and refrigerate 6 to 24 hours.
Combine oil, garlic, seasoned salt, thyme, and ginger in a blender; process until a smooth paste forms, about 2 minutes. Using a sharp knife, score fish skin in a crosshatch pattern. Rub oil mixture evenly on skin and in cavities of fish. Place fish on a large baking sheet; cover tightly with plastic wrap. Refrigerate about 2 hours.
Fill a large Dutch oven (wide enough to fit 1 whole snapper horizontally) with oil to a depth of 4 inches. Heat over medium-high until oil reaches 350°F. Sprinkle fish evenly with kosher salt. Fry fish, 1 at a time, until browned and cooked through, about 10 minutes, carefully turning halfway through cook time. Remove from pot, and transfer to a serving platter. Top with pickled vegetables.
Habanero peppers can be substituted for Scotch bonnet chiles.