"[My progress is due to] mostly Pep," Stones told reporters.
"Definitely Pep, the players I'm playing with at club level, and obviously becoming more mature, knowing myself and knowing the game better. I think the thing for me is how [Pep] has made everything so simple. He has taken my footballing brain to another level. Everyone thinks they know football and different systems but when I turned up at City and trained with him it was like a new door opening that I never thought would be there. Everything seem to click and everything is so simple.
"Simplicity is key. He's very open. He said we can call him or text him whenever I need to – 24 hours a day – he's always said that which is brilliant of him as a person in my opinion. Even if it is not football related. That is important."
Stones also commented on his lack of game time at the Euros two years ago.
"It was disappointing," the Englishman told reporters at St George's Park on Tuesday.
"It was difficult. However long we were out there me and Ross didn't get a second on the pitch. And that is a tournament I can never get back. There's all sorts of ways to look at it. I can look at it and I can be negative about it and almost start pointing the finger and blaming people. But I would never do that. I have got to look at it and think: 'How can I bring that experience into this tournament?' Motivation-wise and knowing how teammates feel when they are not playing. They are just as important as the boys who are playing and knowing that everyone has a vital role to play.
"I think every manager has got that decision [of team selection] to make. I've got to look at it from his point of view and think he is not going to be happy, he probably thought [afterwards]: 'I could have made changes.' It is human nature. We always think: 'Could I have done this, could I have done that?' I just tried to take the positives out of it and the experience for this time around."
When asked whether he has improved since the last major international tournament, Stones replied "Oh, massively, massively."
Stones's England side will face Tunisia in their opening game of Group G in the World Cup on June 18.