This document describes the SMART Teaching 3.0 platform, a mobile-based open platform for English teachers' professional development in Korea. The platform was a two-year nationally funded project that provides online learning through short videos of lessons from expert English teachers on a range of topics. It aims to address gaps in teacher training for Korean English teachers by offering self-directed, mobile-accessible resources focused on practical classroom techniques. The platform includes video clips categorized in four menus on skills like reading, vocabulary, and level-differentiated teaching, as well as interviews and panel discussions.