Slot has been playing Endo out of position this season.
And he said: "I asked Harvey (Elliott) to come into the room before that game (against Tottenham) and he wants to play in that number 10 position. But because of injures I had to play him on the right.
"I didn't even invite Endo in (to the office) because I know he is a 'wherever you play me I’ll do my best' player. That might be normal for a lot of fans to hear but as someone has been around for a while it’s not.
"I know wherever he plays, he gives everything he has. He is a very important player in our team."
On Diogo Jota's form facing Nottingham Forest tomorrow, Slot also said: "You saw the way we built up his minutes. Now he's ready to play 90. It's nice to have him available, so hopefully it stays like this. He's a hard-worker. He tries to become a better player every single day.
"He's a player who is good in both parts. He's a threat when attacking and he works really hard. Jota is an experienced player, which is one reason why he wore the armband. I think he served the club the longest from the players on the pitch. Let's hope he stays fit."