This question is a common one and something you definitely need to prepare for in advance. Research is key—you need to look over the product in question and develop some opinions about it. Including constructive criticism is essential since that’s what was asked for, but don’t be afraid to mention elements you like as well.
Make sure not to bombard the hiring manager with too many ideas, though. As with all of these questions, it’s best to pick an isolated example and explain it well, rather than cover multiple areas less effectively. In other words, always prioritize quality over quantity.
Portfolio and Tools
Walking the interviewer through your portfolio is probably the most fun and most important part of the interview. It’s where you can express your passion and show off your design and technical skills.