Cal. Lab. Code § 5316
Any notice, order, or decision required by this division to be served upon any person either before, during, or after the institution of any proceeding before the appeals board, may be served in the manner provided by Chapter 5, Title 14 of Part 2 of the Code of Civil Procedure, unless otherwise directed by the appeals board. In the latter event the document shall be served in accordance with the order or direction of the appeals board. The appeals board may, in the cases mentioned in the Code of Civil Procedure, order service to be made by publication of notice of time and place of hearing. Where service is ordered to be made by publication the date of the hearing may be fixed at more than 30 days from the date of filing the application.
Ca. Lab. Code § 5316