"After the game on Saturday, it was a kind of embarrassment because we lost 3-0 at home in front of our own fans, which is not good," said the Dutch forward.
"We know they are here to help us in every tough situation but we have to give them something back as well. In the days after that, we were, I don't want to say angry, but we tried to speak together and be honest with each other what we have to do to perform better on the pitch.
"We also know we have to stick together and that's what we will try to do again to put in good performances and get wins.
"Everybody is aware we have to take responsibility on and off the pitch. This was a conversation you have with a team-mate.
"We are aware we have to take responsibility, that we have to do better with certain things on the pitch. That's what we spoke about. We are honest because otherwise there's no point in speaking."
Slot accepted blame following Saturday's defeat, though Gakpo came to his manager's defence ahead of Wednesday's fixture.
"If you win a lot of matches and everything is going your way, you always feel better than when you are losing," he added.
"We know how good we are, we have let that be seen [at times] this season and definitely last season.
"We just have to do better. The trainer takes responsibility for that but the players have a big responsibility to ourselves and the manager and the fans.
"We know what we can do, but we aren't letting it be seen. I definitely take responsibility for it."