Sienna Stark is the founder of Phoenix-based YogieFlow, an online yoga and meditation subscription service for kids – by kids. Stark is just 12 years old and is already on track to becoming a certified yoga instructor. The web-based program, which launched May 1, aims to help kids of all ages elevate their emotional wellbeing and strengthen their athletic ability. “The concept came to me because I’m in my yoga teacher training and I’m a...