Circuits using the LMG342xR030 involve high voltage, potentially up to 600 V. When laying out circuits using the LMG342xR030, understand the creepage and clearance requirements for the application and how they apply to the GaN device. Functional (or working) isolation is required between the source and drain of each transistor, and between the high-voltage power supply and ground. Functional isolation or perhaps stronger isolation (such as reinforced isolation) can be required between the input circuitry to the LMG342xR030 and the power controller. Choose signal isolators and PCB spacing (creepage and clearance) distances which meet your isolation requirements.
If a heat sink is used to manage thermal dissipation of the LMG342xR030, ensure necessary electrical isolation and mechanical spacing is maintained between the heat sink and the PCB.