applying column layout on custom-page.php

Hi,
I think the easiest way would be to alter the query when showing this particular page. Check how to alter the query in Customizr here : https://www.themesandco.com/snippet/three-techniques-to-alter-the-query-in-wordpress/

To organize your content in columns, just make use of the Bootstrap classes, more info about that here : https://www.themesandco.com/snippet/creating-a-column-layout-in-customizr/

Looking forward for your feedback on this, cheers