Creating an air-gapped network that is not connected to the internet or any other networks is the most secure form of physical isolation. This prevents any form of remote access or cyberattack that depends on network connectivity. While using dedicated cabling provides some degree of isolation, it does not ensure the system is fully isolated from external networks. Employing VLANs can offer logical segmentation but not true physical isolation as they still operate within the same infrastructure that could be connected to broader networks. Finally, using firewalls is a security measure used to filter traffic between networks, but it does not provide physical isolation as the system is still network-connected.