The Commonwealth of Australia Constitution Act 1901 begins with a Preamble, then the first 8 Clauses are a British Act of Parliament signed into law by HM Queen Victoria. This podcast series explains the major sections of the Constitution in plain, simple English
You can download the Constitution (26 pages), as well as the Quick and Garran annotated version of the Constitution. Quick and Garran helped write and bring the Constitution into law, so their book helps explain how it was done, what references they used, and much more.