Place pork belly in the freezer until partially frozen, about 45 minutes; this will make cubing easier.

Cut pork belly into 3/4-inch cubes.

Fill a 5-quart cast iron pot 1/4 of the way with water. Add 1 teaspoon Cajun seasoning and bring water to a roaring boil. Add pork belly cubes. Cook until all of the water evaporates and fat renders from the pork, about 20 minutes. Cover pot once fat starts to sizzle and pop; cook and stir until cracklins are golden brown and crisp, about 15 minutes.

Drain cracklins on paper towels. Season with remaining Cajun seasoning.