The best flat water in WA happens to be in the Houtman Abrolhos Islands Pelsardt group. The islands are only 1m high and many of them run East West. Strong wind with no obstructions, no trees and crystal water as smooth as you can imagine. Nice waves on the other side too!
Awesome kiting few have ever seen.
But yep, Alva in QLD, also Bushlands beach in Townsville on the right tide. Augusta is good but gusty, Pelican Point the corner of Woolooware Bay in Sydney in a Southerly, Altona in Vic in the right tide.
And many more, Australia is surely the lucky country.
Good winds,