Hundreds of executives have made the pilgrimage to St. Louis to try to replicate Steve Gund’s elusive feat: He’s the third-generation CEO of a family manufacturer that has averaged 18% annual growth for a decade—all without ever laying off an employee. He said he does it with a leadership model that puts The Gund Co.’s 1,300 employees’ well-being over short-term profits. He has made it his mission to evangelize the approach, especially to leaders of other family-owned companies. “It sounds touchy-feely, but it’s profitable,” said the 55-year-old Gund, whose grandfather, Ed Gund, a former candy salesman, started the composite materials…