On a recent Friday night in Silver Lake, I arrive late to a pottery studio to meet Ella Purnell for a beginners’ class, where, eager to make her first ceramic creation, she has saved me a seat next to her. She’s wearing an oversize New York Rangers sweatshirt, white canvas pants, and sneakers, but just a couple of hours ago she was in full retro glam for a photo shoot in Culver City; her hair is clipped back around her face, maintaining a curl that...