Karanka's appointment was confirmed in a press conference at the club's training headquarters on Wednesday and the 40-year-old's first task will be to pull Boro away from the Skybet Championship drop zone.
Gibson revealed the club thought long and hard about a successor to Tony Mowbray, who was sacked last month, before opting for Karanka, who was assistant to Jose Mourinho at Real Madrid for three years before the pair left last summer.
Gibson said: "Everybody wants to be in the Premier League and it is not easy. Aitor is aware of what is needed and he is aware of the difficulties that can happen in the mad scramble to get there.
"There's no easy answer. We have to work hard and be very clever. What we need is a passage of time to get this club back in the Premier League. We know it is going to take a lot of hard work and a lot of changes."
Karanka's appointment is something of a coup for Boro who currently lie just five points above the Championship relegation zone, with Mourinho insisting recently that which ever club ended up with Karanka would be "lucky".
Karanka, who has also previously coached at national junior level in Spain, was favourite to land the Crystal Palace job but rejected the opportunity to go to Selhurst Park and was instead won by Boro's state-of-the-art facilities.
Mourinho also had a part to play in convincing Karanka to go to Teesside and the new head coach said: "I have been three years with Jose Mourinho and he was supporting me every day. I learned from him and his staff and I think I am ready to start.
"You can learn everything from him on the pitch and off the pitch and in the training room, he's great - he's the one.
"He's a person who was supporting me. I was speaking with him and he recommended to me that I should come here because he believes in this project like me."
Karanka is Boro's first ever foreign coach, but Gibson insisted his appointment was down less to his nationality and more to his desire to cast the net far and wide in his search for the best possible candidate for the post.
Gibson revealed the club had 100 applications for the post and added: "We set down a clear template of what we were looking for and Aitor met the criteria we were looking for. He was the outstanding candidate.
"We needed to freshen up our thinking because the game has changed so quickly in the last five or six years. It was time for change but not just for the sake of change, because it was right to change, and we're convinced of that."