Like many people, Michelle Williams learned a new skill during the Covid-19 lockdowns. The five-time Oscar-nominated actor was researching for her next role in “Showing Up,” director Kelly Reichardt’s film about the Portland, Oregon art scene. At home in New York City, Williams took delivery of a package containing tools and ten pounds of clay. It sat, its heft undeniable, waiting to be molded into something. By the time she was done, it had molded her into something too.