Seongsu has grown into a major commercial district, pushing out residents and everyday infrastructure and leaving the neighborhood precarious. To address this, we reintroduce community-based infrastructure once rooted in Korea's traditional dongne (neighborhood), applying it to Seongsu through small, localized interventions. Starting from Seongsu's red-brick identity, we address the rigidity of conventional brick through Formflex, a flexible brick system produced by local residents. Formflex extends from furniture to structures, connecting spaces while strengthening Seongsu's infrastructure.