By default, when you run openode deploy, it will look for your project structure and find the most appropriate build template (Dockerfile) for your project, and then deploy. A build template (Dockerfile) provides the instructions to build your instance image, which is used to boot up your website. You can also get the auto template manually via:
openode template
To get the list of available templates:
openode list-templates
If you want to use a specific template (non automatic), you can run:
openode template <template ID>
Templates are fully open sources and available here - open to pull requests!