There are two solutions:
1. Using .htaccess with mod_rewrite
DirectoryIndex index.php
RewriteEngine On
RewriteRule ^$ public/index.php [L]
RewriteRule ^((?!public/).*)$ public/$1 [L,NC]
2. You can add a index.php file containing the following code and put it under your root Laravel folder (public_html folder).
<?php
header('Location: public/');