A constructivist learning paradigm emphasises authenticity as a required condition for learning. However, the design of an online learning environment is ultimately separate from learners' real-life environments, it is inevitably challenging to make online learning authentic. In this article, the author aims to propose an alternative way of conceptualizing online learning and its boundaries, based on a double-layered Community of Practice model as a means to facilitate authentically constructivist online learning. The model conceptualizes online learning as interlinked processes of participation and socialization in multiple communities across online- and offline-"layers" of learners' lives. The model guides online course designers in expanding the perceived boundaries of the course environments they design to include learners' offline learning contexts. Instead of having an exclusive focus on providing learners with constructivist learning opportunities within a non-authentic course environment, the model suggests helping learners to engage in more personalized social learning activities situated in their everyday lives. The paper presents data from a series of case studies drawn from the author's work that has examined students' learning experiences in different kinds of online courses, unpacking and answering the central question of what authentically constructivist online learning looks like in each case. With a more holistic conceptualization of online learning, which recognizes and supports online learners' simultaneous presence across internal and external communities, instructional designers may be able to facilitate learners' more authentically constructivist learning experiences.