Press duck legs, flesh-side down, into salt. Lightly sprinkle additional salt on fat side. In a nonreactive container layer duck legs with herbs and spices: Place 3 legs in container, fat-side down, cover with peppercorns, garlic, thyme and bay leaves and press on remaining 3 legs, flesh-side down. Store overnight, covered and refrigerated.
Preheat the oven to 225 degrees F.
Remove legs from container, rinse off salt and seasonings under cold water and pat dry. Place in a medium roasting pan or other pan large enough to hold the legs in 1 layer. Pour the melted duck fat over the legs; they should be completely covered with fat. Cover tightly with aluminum foil and bake until the meat actually pulls away from the bone, 6 to 7 hours. Allow confit to cool in its fat. Store refrigerated, completely covered in fat, for up to 1 month before using.