It sounds as though you are confusing multiple issues. If you created front-page.php, added your content and made the settings in WP for this to display as the front page, then that part of your question is answered.
If the login form and slider are not working on that template, you have a separate challenge to overcome.
The login form and slider are likely relying on JS or other code that is called with the wp_head()
function. As you are not loading your normal header.php file, the wp_head()
function never is called so the dependent script(s) are never loaded.
Try calling get_header()
in your front-page.php temporarily. If the form and slider function, you’ve found the problem.