Hi Sarah, this article only proposes a solution for deploying a NextJS application on a different base path.
While developing locally the base path should not be a concern. You can work locally using root (/) base path assuming your application will be deployed to any possible base path you might want in the future.
In the case you definitively need to run your application locally with the different base path (I guess to run several applications side by side on different base paths) my suggestion is you need to use a reverse proxy. I personally prefer to use NGINX via the Kong distribution (https://konghq.com/) In the post there are examples of this.
Hope this helps.