Folder Structure: You can follow the below folder structure for customize your project and better understanding to playhost

• • Landing
    • bin
    • config
    • public
      • assets
        • css
        • fonts
        • images
        • js
      • index.php
    • src
    • Controller
      • .gitignore
      • HomeController.php
    • Kernel.php
    • templates
    • layouts
      • _footer.html.twig
      • _head-css.html.twig
      • _topbar.html.twig
      • _vendor-scripts.html.twig
      • base.html.twig
      • sidebar.php
      • base-with-plan-body.html.twig
    • All twig Files
    • var
    • .env
    • .env.dev
    • .gitignore
    • composer.json
    • composer.lock
    • symfony.lock