Hi @Peter19,
The link you are referring to is for development of a custom board outside the SDK, not using Zephyr.
Please follow this webpage instead: Board Porting Guide — Zephyr Project Documentation.
As mentioned on that website: "you can usually start by copy/pasting its board directory and changing its contents for your hardware."
The best method to do a custom board implementation using Zephyr based on one of our MCUs is by downloading the zephyr repository using the MCUXpresso extension for VSCode, then going into <Zephyr repository>\zephyr\boards\nxp, identifying the board that implements the same SoC (as the Zephyr guide mentions), duplicating the board and changing the name to a custom name. Then doing all the changes to adjust the files inside this new board folder to the new name, as well as changing the board device tree to the specific hardware of your custom board.
After doing this, the MCUXpresso extension for VS Code will show the new board when importing an example from the Zephyr repository you selected. Once you import a project for your new custom board, building the project as usual will result in the build process creating the runners.yaml file, as well as the rest of the files created specifically for your custom board.
I hope this helps.
BR,
Edwin.
