After the result of the election is proclaimed, but not before December fifteenth nor later than December thirty-first following, the governor, by proclamation, shall designate an adjoining organized county to which the unorganized county shall be attached for judicial, record, and taxation purposes, and all purposes of county government, and such proclamation shall become effective on January first following. If, before such December fifteenth, the board of county commissioners of the unorganized county designates, by resolution, the organized county to which the unorganized county desires to be attached, and if the organized county, before such date, agrees to such attachment, by resolution, the governor, by proclamation, shall declare that the unorganized county is attached to such organized county, effective on January first following the proclamation.