Providing that the board shall be composed of representatives of producers and the public appointed by the Secretary from nominations submitted in accordance with this subsection. If importers are subject to a plan, the board shall also include up to 5 representatives of importers, appointed by the Secretary from nominations submitted by importers in such manner as may be prescribed by the Secretary. Representatives of producers shall be nominated by producers in such manner as may be prescribed by the Secretary. Public representatives shall be nominated by the board in such manner as may be prescribed by the Secretary. If producers or importers fail to select nominees for appointment to the board, or the board fails to nominate public representatives, the Secretary may appoint persons on the basis of representation as provided for in such plan. The requirement for inclusion of public representatives on the board shall not be subject to producer approval, or to importer approval when importers are subject to a plan, in a referendum.