Cut 12 (15x10-inch) pieces of cooking parchment paper. Fold each piece in half crosswise and crease, then open again. Place 1 salmon fillet near fold. Sprinkle each fillet with 1/4 teaspoon each salt and pepper; spread evenly with Dill-Shallot Butter. Top with lemon slices. Fold paper; seal edges well with narrow folds. Place packets on 2 large cookie sheets.