How to create a custom page template in WordPress:
Create a new file in your wordpress theme folder and name it (for example) custom-template.php
Edit the file and put the following code in the top of it:
Template Name: Custom Template
then Save the file.
go into your WordPress control panel, go to Pages menu, click add new, in the left side you will find a box called Page Attributes, from the template option menu you can choose the template file you had created like shown in the following image.
That’s it 🙂