Chris Wood gave Forest the lead before Diogo Jota struck an equaliser for the Reds in the second-half.
Liverpool boss Slot said afterwards: "I am a little bit disappointed, although when you're 1-0 down against Nottingham Forest it is maybe a lot to ask for a win because they've hardly given away any chances in the recent games that they have played. That is why I couldn't ask for more from our players. They created so many chances in the second half but to not score from all of those chances was a little disappointing of course."
On Matz Sels' performance in Forest's goal, Slot said: "He was also like this at Anfield, but also all season. It isn't just their goalkeeper, but the way they defended and because of that maybe they deserved to not concede a second or third goal because they threw themselves for every ball and cross.
"They fight with everything they've got and the fans were really loud and helped them a lot. Still, we managed to create more than a few chances to score and that is what pleased me most and maybe, not for the first time this season, we didn't get what we deserved."
On the result, Slot also stated: "We should be disappointed, although they are having a great season. We want to win every game and they probably want to win every game as well. With how the game went I think we can be disappointed. They are a counter-attacking team and I think we only conceded one counter-attack and for us to come from behind shows the character and quality the team has.
"We must not get a habit of not getting what we deserved because it happened at Tottenham and it happened today and the analysts might not agree but based on expected goals we deserved more than 2-2 draw against Manchester United too."