Rinse chicken under cold running water. Mix water and kosher salt in large bowl, stirring until salt dissolves. Cover chicken with salt mixture and refrigerate overnight (minimum 4 hours).
Remove chicken from salt water brine and immerse in buttermilk. Allow to marinate overnight (minimum 4 hours). Remove chicken from buttermilk, holding each piece to drip excess buttermilk back into bowl. Lay chicken on a wire cooling rack set over a sheet pan.
Mix flour, sea salt, pepper, cornstarch, and potato flour in a large bowl. Dredge chicken parts in flour mixture, shaking off excess. Lay chicken parts on the wire cooling rack.
Using large cast iron, or heavy skillet, melt the lard and butter together and add the bacon or pork shoulder. When the mixture is hot (but not smoking), add the chicken, 1 piece at a time, in a single layer, skin side down. The chicken should be half covered in the butter-lard mixture. Cook each piece 10 to 12 minutes per side, turning once, or more often if necessary, to brown evenly. Dark meat cooks more slowly than white meat. To check for doneness, cut a thigh to the bone and check for redness. When evenly browned, removed the cooked chicken and place on cooling rack. Serve hot or allow to cool to room temperature.