Personas can be an effective means of communicating and synthesizing design ethnographic field data by helping designers maintain focus on users and make sense of complex needs. Personas have however been criticized on scientific grounding and methodological weakness in their creation. Furthermore, few detailed examples of their creation have been published. It is also evident from the literature that there is a methodological gap in creating personas from ethnographic studies. Using a grounded theory approach, this paper offers a systematic and detailed process of creating personas post fieldwork and compares the approach against best practice. Through a case study of design ethnography in product development for people over 65, we reflect on and describe the process in three phases: 1. Post Fieldwork Data Management, 2. Coding and Grounded Theory, and 3. Data Reduction and Data Display, which leads to the final design of the persona. We conclude that using qualitative and grounded theory approaches can assist to strengthen the process of creating personas; however, the time to create and manage the personas increases.