Barca hammered Athletic Club 5-0, with Ferran Torres, Fermin Lopez, Roony Bardghji and Raphinha (2) the goalscorers.
Flick said afterwards: "I always appreciate it when we play as a team, when we play for each other. That's the key. We were in good positions, we created a lot of chances in the first half, and it was really nice to watch. But it's just one game.
"I really value what we did today. We had a great mentality as a team, we defended and attacked as a team. I'm happy because we scored the goals very quickly, it gives you confidence and we were able to control the game. Also, it's good for us to compete this way and create this situation."
Flick was also asked about Robert Lewandowski with his contract running down.
He added, "I don't know what's going to happen. I'm very honest with him, too; I'm very happy to have him. He's playing at a good level, training well, and scoring goals. We have two players in that position who can play—referring to Ferran Torres, who started and scored on Wednesday.
"I'm not going to say he's leaving the team. Why? We'll see what happens at the end of the season."