The Croatian and the rest of his coaching staff were left shocked by the decision in December 2020, because he'd just led the unfancied Baggies to an unlikely and hugely credible 1-1 draw away at champion's elect Manchester City.
The 52-year-old former West Ham and Croatia boss, was shown the door along with assistants Dean Racunica and Danilo Butorovic, as well as first-team coach Julian Dicks.
And Dicks has now told the tale of what actually happened after the game.
Speaking to Ladbrokes he said: "You're travelling to the Etihad to go and play Manchester City, having just come up from the Championship.
"You know it's going to be a tough game, and everybody has to give 100 percent to even a chance of taking anything from the game.
"We rode our luck in that game, don't get me wrong, and (goalkeeper) Sam Johnstone was sensational that night and we managed to nick a draw.
"We were on the coach back home later that evening - we had two coaches, one for players and one for staff - sat at the front, and a couple of the sports analyst lads called me to the back and showed me a story doing the rounds on Twitter claiming we were getting the sack.
"I went 'come on, seriously? We just drew away at Man City.'"
"To be honest, I didn't think anything of it; you know what social media is like.
"But lo and behold, the next day comes and we get called into the office and that was it."
And former West Ham left-back Dick's says that proved the decision had already been made before the Manchester City match.
He added: "Obviously the decision was made before then; they expected us to go to the Etihad, get smashed by four or five and then it would've been an easy decision.
"But it didn't go that way, so clearly the decision had already been made because you just don't get sacked from a club like West Brom off the back of a point away at Man City.
"I don't think the fans took too kindly to the decision, and there's something to take from that.
"It means you've done something right for their club.
"Whatever people think of Slaven, he's a really nice man and he's very good tactically."