Rub duck legs with salt, working it into the flesh and skin. Transfer duck to a medium bowl or airtight container, cover, and refrigerate 8 hours (or overnight). Heat oven to 200°F. In a large saucepan over medium-high flame, heat lard until it reaches 200°F.

In the bottom of a large baking dish, scatter chiles, herbs, and spices. Remove duck legs from the bowl and brush off excess salt. Arrange legs skin-side up in the baking dish. Nestle orange and garlic around legs then pour warm lard over. Tightly cover baking dish with foil. Bake approximately 3 hours and 30 minutes, until bones can pull right out of the flesh. Let duck legs sit in fat until cool enough to handle, approximately 30 minutes.

Transfer duck legs to a dish. Set aside 3 to 4 tablespoons of fat. Remove skin from duck legs and set aside. Pull meat from bones, tearing into 1-inch pieces. In a large nonstick skillet over medium flame, heat reserved duck fat. Add duck skin and cook, turning halfway through, until deep golden brown and crisp on both sides, 12 to 15 minutes total. Transfer chicharrones to paper towels to drain and let cool 5 minutes. Crumble into small pieces.

Heat the oven to 425°F. In a bake-safe dish, add habaneros and garlic and drizzle with oil. Roast until garlic is soft and lightly browned, approximately 8 minutes. Let cool. Transfer habaneros and garlic to a blender and add vinegar, salt, and mango. Blend on high while streaming in ¼ cup water. Once smooth, let cool completely.