Drape cling film over a glass baking dish. Cut salmon in half lengthwise, and place one half in dish, skin side down. Mix together salt, brown sugar and pepper. Sprinkle half of mixture over salmon in the dish, cover with the chopped dill, and pour the vodka over the whole mixture.
Sprinkle the remaining salt mixture over the remaining half of salmon. Place over the salmon in the dish, skin side up. Fold the cling film snuggly over the entire salmon. Place a board over the fish and weigh it down with a heavy object.
Refrigerate fish for 24 to 36 hours, turning every 12 hours. To serve, separate the fillets, and carefully brush off the salt, sugar and dill. Cut into very thin slices with a sharp knife.