Pape Matar Sarr, Lucas Bergvall and Micky van de Ven struck the goals for Spurs on Saturday.
Frank said afterwards: "I think the first 15 to 20 minutes was even. Not too much happened. But then I think we really grew into it and the last 20 or 25, something like that. I think we dominated and created a lot of good opportunities without having too many big, big chances.
"We had really a lot of dangerous situations and we know in football sometimes it's also about getting closer and closer and closer and then suddenly there's that opening where you can score. I think West Ham defended very well first half. It was difficult to get the clear-cut chances but when we got it to Xavi and Mo on the sides and played and run, produced crosses, you know, either in-swing or overlap and so on, and a lot of corners where we also were very dangerous.
"So happy that the goal came second half because you never know, the momentum can change after half-time but we kept going and scored a good goal after and then 3-0 done. So a very good clear win, a good performance and I think we all know the derby and the importance of the game for the fans and I think it's a testament to the boys and the group that we haven't won here in six years.
"It shows everything how difficult it is to play here and now we won 3-0 today. I think that's impressive."
On Bergvall's performance, Frank said: "First and foremost I think his performance was good today. I really like his energy, his pressing skill, his enthusiasm. I think he drags the team with him, in a kind of way. And there's so much he can learn and improve. So I think that's promising as well. Fantastic goal. Well-timed run. Top ball from Romero. And a well-executed header."