Plymouth were bottom of the second-tier Championship when they knocked out the then-Premier League leaders in the fourth round with a stunning 1-0 win.
The Dutch coach also emphasised the FA Cup's significance now that Liverpool are no longer competing in the League Cup, having been eliminated earlier this season.
"I can guarantee you that on Monday you will see all the players that you saw (on Thursday against Arsenal), maybe with some substitutions but then they will be on the bench. So that is going to be different than last season against Plymouth," Slot told reporters.
"Last season I made the decision that some players needed to rest in the FA Cup because you cannot play every player every single time. But it's obvious that we're not in the League Cup anymore. The FA Cup has always been very important for us."
Slot also acknowledged Barnsley pose a genuine threat, noting the Yorkshire club's last visit to Anfield ended in a 2-1 victory in the FA Cup.
"Barnsley, I was just informed, the last time they played against us, they beat us. That was in 2008, in our stadium. So we take them, as we took Plymouth, very seriously as well," he added.
Liverpool were also dealt a blow after right back Conor Bradley was potentially ruled out for the season after his knee injury at Arsenal, with the Northern Irishman set to undergo surgery.
Slot also said striker Hugo Ekitike is "not 100%" but that the club would "do everything to have him available" for Monday's game.
The Dutch boss said Federico Chiesa remains an option, but his participation would depend on Ekitike's availability.
"I spoke to him (Chiesa) two days ago and he said to me that he played more in the recent weeks than he ever did before under me," Slot said.
"But he is one of the players that could feature in that game, definitely. But Hugo might be back, so let's see how we will start that game. He is one of the options that I have."