Slot was speaking after last night's 1-0 defeat to Preston.
He told LFC-TV: "After two weeks of tough training sessions it's important to play a game as well. The most important thing is everybody was fit before the game and they stayed fit during the game as well.
"It's been a good two weeks. Unfortunately the result today was not what we wanted. But they stayed fit, many of them got minutes, also a lot of young players got a few minutes so that was a good thing."
Slot added: "Every session and every game gives you new ideas where you have to work on. But we have to understand 11 players of the ones who played many, many minutes last season are not even in the building yet.
"It's good to see some young players again today showed some good things. And the players we have (available) who played many minutes last season, they stayed fit, showed some good things today and in the last two weeks, so that's something to take into our USA tour."