Sensory technologies alter how we perceive our body, which can have profound implications for multiple domains. Prior work has contributed a myriad of artefacts and evaluative studies, but we still lack design knowledge to design meaningful body perception alterations facilitated by sensory technologies. To address this gap, we draw from soma design to propose a methodological approach centered on body sensations as design material. We articulate our approach based on a project on co-designing wearables to alter body perception together with professional dancers. Our approach involves engaging participants in articulating and sharing body sensations to others, and exploring somatically sensory stimuli to co-design concepts for future technologies. We contribute experiential facets of body sensations, movement and sensory potentials to alter sensations, methods and design strategies, and a collection of ideas. Our work can be relevant to design communities interested in sensory technologies, perceptual alterations and body sensations as material.