Any notice to be given to any person under or pursuant to this Act or any regulation must be given in writing either by delivering the same to such person, or by leaving the same at or posting the same addressed to him at his usual or last known place of abode or business in Western Australia, or, if he is unknown or has no place of abode and no place of business in the State, or cannot be found in Western Australia, then by affixing such notice in a conspicuous place on the land to which such notice relates.