I believe it is understated how much Slaf really is an unique prospect. His size and skill combo allowed him to play a very individual game growing up, but he's learning how to play collectively in the NHL.
Yes, it's scary that a 1st overall selection is a project of that magnitude, but they knew exactly what they were getting into when they drafted him. Slaf seems to have the mental make up (delayed gratification mentality) that is very very uncommon with kids his age nowadays.
They're hoping to develop his ability to generate off the puck, both in transition and in-zone play, which will complement his instinctual power game and make him a very impactful player offensively.
I honestly believe a player like Dach can help him a lot, because Slaf's main weakness is Dach's main strength.