Set a default site layout with the Genesis Framework.

functions.php

<?php
// Do NOT include the opening php tag

// Set content/sidebar as the default layout.
genesis_set_default_layout( 'content-sidebar' );

// Set sidebar/content as the default layout.
genesis_set_default_layout( 'sidebar-content' );

// Set content/sidebar/sidebar as the default layout.
genesis_set_default_layout( 'content-sidebar-sidebar' );

// Set sidebar/sidebar/content as the default layout.
genesis_set_default_layout( 'sidebar-sidebar-content' );

// Set sidebar/content/sidebar as the default layout.
genesis_set_default_layout( 'sidebar-content-sidebar' );

// Set full-width content as the default layout.
genesis_set_default_layout( 'full-width-content' );