After Luis Diaz opened the scoring, West Ham grew into the game and equalized in the 86th minute with an Andy Robertson own goal.
However, captain Virgil van Dijk quickly restored the Reds’ lead, powering home a header just three minutes later.
"That is what we've done the whole season. After the disappointment of being knocked out by PSG (in the Champions League), we show up again, show up every three days, with this mentality," Slot told Sky Sports.
"We don't win games the easy way. The easy way is taking control of the ball, pass it around five times and we have a goal and the next goal and the next goal.
"If we achieve something this year, it's mainly to do with the mentality the players have shown. That's what you saw today as well."
With a 13-point lead over second-placed Arsenal, Liverpool need just two wins from their last six games to secure a second Premier League title and their first trophy under Slot.