VietTESOL International Convention 2026

English teachers in EFL and ESL contexts increasingly need classroom tools that reflect local curricula, learner needs, and constraints such as limited bandwidth, shared devices, and unsustainable subscription costs, yet commercial applications rarely meet these specifications. This 60-minute workshop demonstrates a replicable workflow in which language teachers, without prior programming backgrounds, design and build their own single-file web applications using artificial intelligence coding assistants. Grounded in constructionist learning theory, the technological-pedagogical-content-knowledge framework, and recent research on teacher agency in CALL and mobile-assisted language teaching, the session argues that teacher-built tools achieve higher contextual relevance and pedagogical alignment than off-the-shelf products, while remaining free, offline, and fully under teacher control. In the first 15 minutes, the facilitator showcases three applications already used in Vietnamese classrooms: a vocabulary studio that turns chatbot output into interactive flashcards, quizzes, and word-match games; an interactive whiteboard with timers and embedded reading materials; and a colour-coded writing feedback annotator built around an evidence-based corrective feedback taxonomy. Each demonstration unpacks the pedagogical rationale, the prompts and design decisions, and the iteration cycles behind the build. In the remaining 45 minutes, participants work in small groups, scope a real teaching problem of their own, draft a structured development prompt, and use a coding assistant on a laptop or projected screen to produce a runnable prototype. Participants leave with their own prototype or detailed blueprint, a curated prompt library, and a sustainable model for ongoing teacher-led tool development.