Darwin Nunez struck twice in injury-time for the 2-0 triumph.
Slot said afterwards, "Yes, of course I had doubts about that because before we scored the two goals it felt as if I was looking at the same game again and again and again and in the same pattern. I said it already a few times in other interviews that against (Manchester) United everybody was focused on the (Harry) Maguire chance but (in) the seven minutes before we had three open chances.
"So many times in recent weeks – against Tottenham as well – we missed a lot of chances, against (Nottingham) Forest we missed a lot. So, it would have been a bit surprising if I felt, 'OK, after all these chances missed today, we will probably score in the last five minutes.' But the players proved me wrong again."
On Nunez, he said: "(A reporter) asked me similar things before the game about Darwin and I didn't agree then that he's not having a good season. I think he's having a good season, where he scores goals, he works very hard for the team, he assists. But he's in competition with a lot of good players, so that's why he's not every single game on the pitch.
"But I'm very happy with him – not only because he scored today two goals but that, of course, helps – but I'm very happy with the other performances he put in for us as well.
"The first one was a long build-up, the second one was a counter-attack. He can, of course, score his goals against a low block because he's a striker and he's a threat in crosses as well. Immediately after he came on, he had quite a good chance when Robbo (Andy Robertson) crossed it in.
"But if it's about strikers or if it's about the team, if we would not have scored today in the last five minutes then the headlines would have been Liverpool drops points again and no-one would have told you (about) 37 shots on target. What a display. How many teams were able against Brentford to have 37 shots on target during a game? And now because of us scoring two, there is probably a bit of emphasis on that fact as well.
"So, this is the industry we work in. As a manager, the team, the players, we all accept this and we all understand that there is a lot of focus on if it doesn't go well and not as much on the fact if you have a great performance. We are in an industry where it's about winning and losing – and not about if you play beautiful football. People only enjoy good football, beautiful football if you win. And otherwise, there's no focus at all on the performance."