Slater went over straight from a scrum to double his tally but Fiji winger Suliasi Vunivalu halted the one-way traffic when went over for his ninth try of the tournament, becoming the first player to score points against Australia in their last 10 matches.
No wonder Suncorp Stadium was only half full, this game never looked like being much of a contest and the blowout only goes to show how disappointing the Kiwis were last weekend, by not being able to score any tries against Fiji.
Fiji looked lively early and took the lead with a sixth-minute penalty goal. Fiji scored one in their last two games.
On fourteen the Aussies made their pressure tell when Billy Slater was one of three men on a massive overlap left to take a pass ten metres from the line and walk over.
Holmes' second and fourth tries came off simple attacking shifts, but the highlight was a 90-metre intercept in the 42nd minute where he outlasted Vunivalu and Akuila Uate. Koroisau failed to add the conversion and the Bati trailed by 40-6.
He broke his own record for tries in one match with his six against Fiji - and in doing so surpassed fellow Australian Wendell Sailor's record for tries at one World Cup.
This was clinical from Australia but you still felt that they'd left something in the tank for next weeks final.
Australia fullback Billy Slater grabbed his 15th and 16th World Cup tries to better the career record for the tournament he previously shared with Jarryd Hayne, the 12-cap Kangaroo who turned out at stand off for Fiji on Friday night. There were good patches from Fiji, especially when muscling up, but Australia just wore them down by completing their sets and not making mistakes.
Winger Valentine Holmes followed up his five-try feat against Samoa with a six-try haul against Fiji to propel Australia into the World Cup final.
Australia: Slater (2T), Gagai (2T), Chambers, Dugan, Holmes (6T), Morgan, Cronk, Woods, Smith (7G), Klemmer, Cordner, Gillett, McGuire.