Sounds like what you want is a Custom Page Template It’s quite simple, if you want to call your layout “My Special Layout” just create a file in your Theme Directory calling it whatever you like (I’d call it “page-my-special-layout.php” but that’s not required) and add the following comment to the top of the template file:
<?php
/*
Template Name: My Special Layout
*/
After the comment put in whatever HTML you need to design your desired page.
Then once you have the Template in your Theme directory and you load the Page Editor in the WordPress admin console you’ll be given the option to assign it as your Page Template; simple as that:
