The Germany international hasn't scored nor laid on an assist since his £125m arrival from Bayer Leverkusen.
But Slot, ahead of today's derby against Everton, said: "He is an artist, but he can be mean as well. Otherwise, you can’t reach the levels he's reaching. He works incredibly hard here in this building to get better and better and better.
"So that mentality he has inside of him and you also see that mentality when he loses the ball once or twice. He's not going to hide, he wants the third one, he wants the fourth one. In general, it's not just about Florian, we have to play three games in seven days.
"And if you've watched what we did on Sunday and what we did on Wednesday, we are trying to manage to get them all fit through these three games because it's not a present that we got to play in the beginning of the season three games in seven days."
Slot insists Wirtz doesn't have to live up to his price-tag.
He continued: "We (don't have) long conversations (about fees). Sometimes you see when you pass them or in a remark like: ‘Virgil, if you put inflation to that, he would be just as expensive as you’.
"And then I say: ‘Listen, Trent Alexander-Arnold was £10m for a one-month contract (to join Real Madrid for the Club World Cup), multiply that by 12, you come to 120m‘. So it's just where we are.
"He only had a one-year contract (left at Liverpool), so what happened if we would have sold Trent when he had two years to go? Then we would have been £240m. So it is just the new reality.
"We face a player tomorrow that's been bought by Manchester City for £100m (Jack Grealish), and that's now at Everton. So this is the world we are living in and I don't think it is something we speak about a lot, but sometimes in a joke or in a remark."
Doing things differently
The Reds boss added: "What is different for Florian is that he went to a new club where we probably do things a lot differently on and off the pitch. It is not Eredivisie, and I think the Bundesliga is in between Eredivisie and the Premier League.
"So maybe that's also the reason why he and Hugo Ekitike loved to come here because they want to make the next step in their career. But he's adjusting, in my opinion, very well.
"He always wants to have the ball, even if he has a few moments where we feel like he could do better. He just always wants to keep the ball, always keeps on trying. And he gets better and better, and fitter and fitter.
"That's maybe the thing that matters most, because we don't have to teach him how to play football. He just has to adapt to the intensity levels of the Premier League.
"As much as I like him and as much as I think he's a good player, we have so many good players that are already here. So I don't think he's at a level so far above the rest that he sees things the rest do not see. Then we would be too negative about Virgil, Mo, Dom, Mac Allister.
"We have all these players who are top, top, top level, and they have to get used to each other. I don't think it is about him or someone else seeing things others don't see.
"They're all at this incredible level, but as it is in football, no matter how good you are, you have to get used to each other.
"What do you want? When do you show yourself? Trent and Mo were a great example of that. If Trent opened up, Mo already knew to make a deep run because he will play in behind. These kinds of things you get from playing a lot together.
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"So, yeah, as much as I think how good of a player he is, I wouldn't put him up there with the rest over there. That would not be fair to the rest of the players, and also not fair to him.”