I was a little nervous about this interview due to reading articles about UNIQLO generally being a strict workforce, especially when it comes to interviewing amongst hordes of people, but this was a great experience, personally.
I applied online via Indeed.com and received an email the morning after inviting me to an interview for the new WA store. A few days later at the time I scheduled myself for, I arrived way early to the interview (in anticipation of a huge group), but I was surprisingly the first one there and was able to meet the assistant manager beforehand and wait for the scheduled time to start. Only two other applicants showed up and it was the three of us who interviewed. We were asked to introduce ourselves and note our availability (must have two closing shifts during weekdays and also weekend availability, period). She basically asked each of us the same amount of questions (all different) in a differing order and walked us out after asking if we had any questions (please ask some!). Overall, a positive experience. I recommend smiling, dressing well, nodding and appearing enthusiastic, trying to sound conversational instead of reciting your life story or random factoids, and be authentic! Also, definitely do some research about the company. They WILL ask.