Wirtz, who cost £125m, was left out of Liverpool's squad for their preseason friendly against Preston at the weekend.
Klopp, now the global football director of Red Bull, believes Wirtz will establish himself in the team, but is unsure which position Slot has in mind for the player.
Wirtz is a versatile player who can play across the front three and has also been used in a central attacking midfield role by Bayer Leverkusen.
Klopp is positive about Wirtz's signing and thinks it will be beneficial for Liverpool, despite the team being champions.
"This is going to be absolutely fantastic," Klopp said. "I'm sure of it. It's very hard to strengthen a team when you're champions, but Liverpool have managed it."
He added: "They've signed an exceptional talent in Florian Wirtz. I'm looking forward to seeing it. It's going to be great."
