As others have commented, a gap in your resume shouldn’t even be a part of the conversation since it’s just an absence of anything that would be relevant to the hiring process. Doesn’t mean you won’t be asked though, unfortunately, and I have experience being the candidate with a long gap, so I can tell you how I handled this.

Sitting on the hiring side of the table, my only concern is that you weren’t just twiddling your thumbs. If you had personal matters to take care of, unpaid projects to focus on, family to look after, that is all part of life and none of my business. When explaining my own employment gap, I was frank about how my previous appointment had taken its toll on my mental health, and that I wanted to reconnect with other aspects of my life before taking on another role. I didn’t go into any specifics, but made sure to mention that part of this time was spent studying stuff that’s relevant in my field and exploring emerging technologies.

No matter how long a gap, it’s not something you should acknowledge or attempt to explain in your resume or cover letter, and it’s not something you need to bring up yourself in the interview. My view is that it’s bad etiquette to even ask, and you should try to adopt this mentality yourself so that you project confidence if you have to answer the question. You have nothing to hide or be ashamed of. Your life is more than your CV.