There are lots of web pages with advice on how to do this, but they all seemed annoyingly complicated, and sometimes the advice is outdated, so I figured out my own simpler solution. This advice is good as of December 2017, so it should last all through to the official release of Alexa in Australia when all this hoo-ha will be unnecessary.
The first advice you’ll usually get is to install the Alexa app from the US App Store by doing a complicated dance with Apple to create a second App Store account whilst pretending to be in the US. You don’t need the app! The Alexa web site does everything you’ll need.
To start, go to https://alexa.amazon.com/ and log in, then go to Settings, then “Set up a new device” – there are instructions for every type of device. Basically this takes you through the old school way to set up a device, putting the Alexa device into hotspot mode, connecting to its network then pulling up a config page where you can tell it how to get on your WiFi network.
Once you have the Alexa on your network, the next hassle is to configure the settings on your device so it knows you’re in Australia and gives you the right time and weather. I independently arrived at the same solution for this that these guys did, so rather than me redoing all their nice work, just go there and follow their instructions. It looks a bit scary but it’s not hard – if you’re a web dev like me and therefore used to fiddling with pages in Developer Tools in Chrome you will feel right at home.
Enjoy your new localised Alexa device!