You can override the default layout option with the filter
Shorthand version: (note that this only works with the six built-in Genesis layouts, not ones you create yourself)
For a more robust way to control your site layout, you can use this filter in conjunction with conditional tags or the template hierarchy.
Because this filter overrides the default layout option only, you’ll still be able to select custom layout options for individual Posts and Pages, via the Layout Settings section of your Post or Page editing screen.
genesis_pre_get_option_site_layout is located in lib/functions/options.php.
Relevant tutorials from the Genesis community.