A blog layout should also have an inner page to show single posts. You could store the layout in layouts/blog_inner.php. Another option is to keep it in the template root folder and use it as a default layout for posts in all pages. Editable regions and a comments module would seem appropriate for such layout.
Examplelayouts/blog_inner.php
Example Shop Layout
If we want to have a shop pages in out template we will need to make a shop layout and a layout to display products from the shop.
The shop layout is created by including is_shop property in the definition of the layout file. You can add products only to pages that are defined as shop by using a shop layout.
Make a new file at userfiles/templates/my_template/layouts/shop.php, this file will load when you create new page and choose the "Shop" layout.
Exampleshop.php
The categories, shop/products and shop/cart modules are now rendered by the layout.