I've set my first sandbox up as a Next.JS project in its own folder, so you can start each one by navigating into the correct directory and running yarn start (or whatever command you configure to spin up the server).

@Kiran, if you want to create your own single directory for all the sandboxes (or even build inside mine), that's totally fine. Or you can keep the pattern going and create one directory for each sandbox environment (eg. email vs social media vs drive).