Raphinha and Lamine Yamal both scored twice, with Fermín López and Anthony Gordon also finding the net as Hansi Flick's side produced an emphatic response to consecutive defeats against Paris Saint-Germain and Real Madrid. Mariano Díaz scored Alavés' consolation.
Flick was particularly pleased with the way his players controlled the contest, having anticipated a difficult afternoon against an opponent prepared to defend deep and attack on the counter.
"We expected them to defend well and run in transition. We controlled the game and were focused defensively. I'm happy with how we played, especially in the first half," the Barcelona coach said.
The German also praised the performances of his attacking players, with Raphinha, Yamal and Fermín all influential.
"When you score two goals, it is easier to come out," Flick said of Yamal. "I had spoken to him at half-time. He needs to regain his confidence in one-on-one situations. It is important that he rests. It was a very good performance from him.
"I'm delighted with his level, and with Fermín and Raphinha. That is what I wanted to see after the defeats. Our reaction was good."
Barcelona were four goals ahead by half-time, with Raphinha opening the scoring before Fermín doubled the advantage. The Brazilian then added his second, and Yamal made it 4-0 before the interval. Yamal scored again after the break, while Gordon completed the rout late on. Mariano pulled one back for the visitors.
Flick also highlighted the contribution of Brian Fariñas, who made his first-team debut at right-back amid Barcelona's defensive injury problems.
"I'm very happy with his performance today. He plays at a good level. He is well connected with Lamine, and that is very important. He helped us a lot. He deserved to play. He is very professional and always very focused," Flick said.
Frenkie de Jong was another player asked to adapt, operating in central defence because of the number of unavailable defenders.
"We have to think differently because we have four defenders out injured, and we hope they return soon. But we don't know when that will happen. I asked Frenkie if he could play at centre-back and he said yes. I appreciate that."
At the other end, Quique Sánchez Flores was left frustrated by Alavés' lack of resistance and accepted responsibility for the heavy defeat.
"I have the feeling that every time they had an action that could lead to a goal, it did. We were not tough or decisive enough. We apologise. As coach, I take responsibility for the defeat, and more than ever I am alongside my players," he said.
The Alavés manager felt his side had made Barcelona's task too straightforward.
"When you imagine a match against Barça, you imagine this kind of game. We opened the door for them and gave them opportunities. We were not decisive. We lacked aggression and did not make things difficult for them."
Sánchez Flores also insisted that the criticism should be directed towards him rather than his squad.
"We leave frustrated. I want the criticism to fall on the coach, not my players."
He acknowledged that Alavés had been unable to impose themselves, despite having some opportunities when the score was 2-0.
"We had chances after the second goal and got into dangerous areas. But then the other two goals condemned us. We will get back up."
The defeat was painful, but Sánchez Flores urged his players to move on rather than allow one poor performance to define their season.
"It leaves a mark. We have to understand that we could have been better, but this is temporary. We cannot remain stuck in the mistake. We have to turn the page."