This study explored an innovative coaching model termed "video-based online video coaching." The innovation builds from affordances of robot-enabled videorecording of lessons, accompanied by built-in uploading and annotation features. While in-person coaching has proven effective for providing sustained support for teachers to take up challenging instructional practices, there are constraints. Both logistical and human capacity constraints make in-person coaching difficult to implement, particularly in rural contexts. As part of an NSF-funded project, we studied nine mathematics coaches over four years as they engaged in video-based coaching with teachers from geographically distant, rural contexts. We adapted a content-focused coaching model that involved a collaborative plan-teach-reflection cycle with synchronous and asynchronous components. The planning and debriefing sessions were done synchronously via Zoom, while the teaching and initial video reflection on teaching via annotations were done asynchronously. We focused on the coaches' practices in each part of the coaching cycle by analyzing interviews, surveys, annotations of the video, and transcripts of the planning and debriefing sessions. We found that: features of the online environment enabled the coach-teacher pairs to collaboratively discuss the mathematics and how students engaged with the mathematics; the coach used video and annotations to help teachers reflect on specific aspects of their practice; and the coach-teacher pairs formed trusting and productive relationships despite not having met in-person during the duration of their work together. Our findings showed that the online platform is not only an effective implementation for coaching, but also affords new opportunities for teacher reflection and evidence-based discussions.