This article explains how to create a Gmail alias, whether you want a temporary or permanent alias.

Gmail ignores certain characters in your email address, but most other websites do not. This means you can “hack” your email address to create potentially dozens of aliases for use on almost any website. And yes, it’s free (and very easy to do)!

Here's how to make them:

Type your email address wherever you want to use the alias, for example in a text box on a new user form on a website.