I'm not sure if the interview process varies by store/region, but I will tell you how mine went. I applied on a weekday afternoon and received a call from the design center manager within a few hours. I went in for Interview #1, which was a normal one-on-one interview with the store manager. She called me back for Interview #2 within a few days. During that 2nd interview, I had to take a DESIGN TEST. She also talked to me about the importance of personal style and fashion and gave me the instructions for my drug test. I was then called in a 3rd and final time so they could offer me the position and talk specifics in person. That day, I was told I had to purchase a certain fashion book, read it, and then buy an entirely new wardrobe so I would have "the look" they want to portray. (My clothes were professional, modest and fashionable to begin with... but what I gathered was they wanted me to wear gawdy jewelry, bulky scarves, fake nails, boots, designer handbags, etc.)
******(Interview #2) There is always a design test. Sometimes it's done on the same day as Interview #1. They will give you some graph paper and a little info packet about a fake client-- their room dimensions, lifestyle, budget and what they're hoping to accomplish. They then give you up to 2 hours to draw the room, lay out the furniture, select furniture, customize furniture, sketch up custom window treatments and pillows, select accessories and lighting and present this project to some of the designers (who pretend to be the clients) so they can see your design and selling skills. They will pick you apart. They want to see how you handle criticism.