The Citizens lacked penetration before the break and failed to seriously test Tigers keeper David Marshall in the opening 45 minutes at the KCOM Stadium.
They finally found the breakthrough 18 minutes from time when Yaya Toure converted a penalty, conceded by Andrew Robertson for a foul on Raheem Sterling.
Substitute Kelechi Iheanacho doubled the Citizens' lead soon afterwards and an own-goal by Curtis Davies in stoppage time sealed the win.
But Guardiola was critical of his team's performance in the first half and had some words for his attackers during the interval after failing the breach the basement club's goal.
"The first half was quite good in terms of control – all accept the last five minutes when we conceded stupid faults and they create a lot of problems especially with [Robert] Snodgrass because of the quality of his set-pieces," the Spaniard said in his post-match press conference.
"But we forgot in the first half that the goal was there. Every time that Raz [Sterling] has the ball we just pass, pass, pass and we don't need Raz for the pass – we need his quality in one against one.
"In the second half from the beginning he arrives at the byline and he created the penalty. In the first action he created the third goal.
"At the end we finish with another counter-attack because the game is almost over and the opponents are not set up to defend. Of course, we are happy to win again, especially away here at Hull."
Guardiola added: "I spoke with the strikers, all of them. The wingers have to be the wingers. You have to try to dribble and attack the goal. In the first half we didn't do that; in the second half it was much, much better."