Immediately after the last day fixed for filing of such nomination petitions with them, the Secretary of the Commonwealth or the county board, as the case may be, shall fix a day for the casting of lots, in such manner as may be prescribed by the Secretary of the Commonwealth, or county board, as the case may be, for the position of names upon the primary ballots or ballot labels. The Secretary of the Commonwealth shall give at least two (2) days notice by mail of said date to all candidates whose petitions have been received and filed in his office, and the county board shall give at least two (2) days notice of said date by posting thereof in a conspicuous place in its office, and by publication once in at least two newspapers of general circulation published in the county. All candidates may appear in person, or by agent duly authorized by letter of attorney, signed and acknowledged by an officer empowered to take acknowledgments. In the event of any of said candidates not being present in person or by representative at the time of casting of lots, it shall be the duty of the Secretary of the Commonwealth or the county board, as the case may be, to appoint some person to represent such absentee. After said lots are cast, the Secretary of the Commonwealth or the county board, as the case may be, shall accordingly establish the order in which the names of said candidates are to appear upon the primary ballots or ballot labels, and certify the same for placing upon the official primary ballots or ballot labels.