The author repurposed an old phone as a server to run personal infrastructure, including a remote browser and finance tracker, after rooting the device and installing Termux and other necessary software. The phone's hardware and Android operating system are utilized to manage the server, with a custom setup to ensure reliable and efficient operation. The author notes that this approach can be a viable option for running personal services, especially when considering the cost of traditional VPS solutions. The setup includes measures to mitigate potential issues, such as battery degradation and heat management.