We may receive a commission on purchases made from links. If you own an Amazon Fire TV device (e.g., a Fire TV Stick, a smart TV that uses Fire TV ), you're sitting on a trove of over 400 free live TV channels. There's an app built into the Fire TV interface called Fire TV Channels , and it's Amazon's take on a FAST (Free Ad-Supported Streaming Television) platform. The app is supported by hundreds of media providers, including major networks like ABC, CBS, FOX, and NBC. It also gives you access to live and on-demand content from channels like CBS Sports HQ, ION, America's Test Kitchen, and more.  Using a FAST service like Fire TV Channels is a move that more and more households are making, and the main reason is cost. Not only is Fire TV Channels 100% free, but you don't even need to create an account to start watching. Fire TV Channels is also a great way to replace cable, and it's arguably a better, more option-packed alternative to over-the-air (OTA) broadcasts.…