<?php get_header(); ?>

<?php
/*
Template Name: Custom Category Page Template
*/

$args = array(
    'category_name' => 'my-category-slug',
);
$query = new WP_Query( $args );
if ( $query->have_posts() ) :
    while ( $query->have_posts() ) : $query->the_post();
        // your post content here
    endwhile;
    wp_reset_postdata();
else :
    // no posts found
endif;
?>

<?php get_footer(); ?>