Soliola was on Tuesday night suspended for five games for the dangerous contact that knocked Slater out.
Evidence from Melbourne's head medical official, Dr Jason Chan, claimed the Maroons fullback was "unconscious before he hit the ground".
"Billy knew he was in Canberra, but not that he was at GIO Stadium or why he was there," the report said.
"He had no recollection of previous two weeks. Not aware he had played State of Origin, or that he had injured his ankle that week."
During a 100-minute hearing, the NRL's counsel, Anthony Lo Surdo, demanded a message be sent by the way of a lengthy suspension for the foul play.
Lo Surdo also claimed Slater "had no opportunity to protect himself", as he called for a six-game ban that would've ruled Soliola out for the season.
"He was in an extremely vulnerable position," Lo Surdo said.
"He was not expecting to get hit the way he was hit."
But Soliola's defence lawyer Nick Ghabar accused Chan of speculating as to when Slater was knocked out, and claimed the fact Slater slipped had much to do with the high nature of the hit.
"Within fractions of a second he has dropped markedly ... at least 20cm," Ghabar said.
"Contact would've been hip or shoulder height."
He also argued Slater's slip had prevented himself protecting himself as he fell to the ground, while Soliola claimed it "would've been very hard" to pull out of the tackle.
However, the three-man panel of Bob Lindner, Shaun Garlick and Mal Cochrane took just five minutes to agree on the five-game ban.
The suspension marks Soliola's first in either the NRL or English Super League since his debut in 2005.
He will be available for the last round of the NRL season when the Raiders take on Melbourne.
Meanwhile, NRL referee Matt Cecchin escaped sanction for failing to send Soliola off for his sickening hit on Slater, because he was unsighted.
Senior NRL review official Bernard Sutton and assistant on-field referee Chris Butler were both demoted on Tuesday.
But Cecchin will officiate in Friday's NRL clash between the Warriors and Cronulla, as it's understood he was following his duties as lead referee in watching the ball as it was passed across the field.
"The officials who were ultimately responsible for the decision, given it occurred in backplay, were the senior review official and the assist referee," Archer said.
"As a result, Bernie Sutton will not be a senior review official in round 21, and Chris Butler will officiate in Queensland Cup.
"It is my expectation that the assist referee firstly identifies incidents in back play, while the senior review official should have taken stronger action due to the serious nature of this incident."
As a result, Sutton will drop back to the role of regular bunker reviewer, and will have all his major decisions overseen by senior official Luke Patten.
Regular review from Saturday night official Bryan Norrie has also escaped punishment. He'll work with Cecchin in Friday night's clash from the bunker.
Cecchin is considered one of the NRL's most senior referees, having officiated in this year's State of Origin series and the 2016 grand finale.
Archer was particularly critical of the decision not to send Soliola off after the dangerous tackle, which floored Slater and ruled him out for this week's clash with Manly.
The former on-field referee released a statement after the game, declaring it had met the indicators required for a send-off.
Photo by: MARK NOLAN/ GETTY IMAGES (Melbourne Storm star Billy Slater is carried from the field after being knocked out in NRL round 20 match against the Canberra Raiders).