Ok, I won this game, but this is not the point. The position is closed and stockfish is not very good at closed positions, so if a human would answer, I'd appreciate it.
White's 24.f3 - 25.g4 pawn break is clearly a decisive mistake, but what if white didn't go for it? I don't think he has any way to make progress here but what if he just stays behind his pawns, how do I crack him open? I was considering maybe marching the king over the queenside and going for b6, is that the right way to do it?
24 f3 25 g4 as no mistake, it is the correct plan to activate the incarcerated rook Rh3, but at that point black was already winning.
18 Ng4 and 19 Nxf6 was wrong: why trade the excellent central knight outpost and spend two tempi on that.
If white had activated his other knight Na2-c3-a4-c5 then white would stand dominating.
Well, the only rook this pawn break activates is mine. And that's not at all what I was asking. Otherwise, thank you, Captain Hindsight.
Analysis is always hindsight.
What were you asking?
"White's 24.f3 - 25.g4 pawn break is clearly a decisive mistake"
No it relatively is the best, only the 25 g4 should be prepared by 25 Kf2. White was already doomed.
"what if he just stays behind his pawns, how do I crack him open?"
...f6, ...Rae8, ...e5
"I was considering maybe marching the king over the queenside and going for b6, is that the right way to do it?"
If you march your king towards c7 to play ...b6, then the exact plan of f3 and after preparation g4 counters that.
20 g3 is absolutely dreadful. I would give up the pawn rather than do that.
I think that after what happened in the game 22. Nxf5, you can't really make much progress, I mean your position is better but I don't think you can convert that the position. Only accessible pawn breaks are b6 and e5 problem with b6 is that it creates weakness and does not give you anything, pressure from the half open b-file means nothing after he plays c3 and e5 is just unachievable if your opponent prevents the threat by rook e1 or getting the knight to d3. Instead of Nxf5 you should have doubled your pawns by taking 22. exf5, this gives you the open file which only you will be able to use to your leverage it also provides a solid control of e4 and restricts all his pawn breaks on the kingside. By 22. exf5 since the pawn structure is symmetrical and static there will be a lot more emphasis on piece play in which you are clearly superior