Just don't talk negatively about your old job. "I'm looking to move because I want to have more impact". "The work I'm doing now is not core to company's success and I want to have more impact". Etc.
I never looked down on someone who was doing boring work if that is what they were supposed to be doing. I'm looking for people who can communicate well and have strong core fundamentals. If you can demonstrate those things then you're doing well.
What kind of red flags are you worried about?