After designing an application with Lovable, users can deploy it using a preview link or opt for custom domains via platforms like Vercel or Netlify, with the latter supported through a detailed guide provided in the text. To deploy with Netlify, users must first transfer their project to GitHub using the Lovable editor. They then log into Netlify with their GitHub credentials, authorize access, select the appropriate repository, and deploy it. Custom domain configuration in Netlify involves managing domain settings, verifying the domain, purchasing if necessary, and setting up DNS. A netlify.toml file is recommended for proper routing, and the Lovable app will automatically redeploy on Netlify with any changes, providing a seamless integration experience.