You can hide your taskbar using Windows 11 settings, but that won't hide it completely. The only way to do that is to use a third-party application.

Hide Taskbar is freeware that lets you hide only the taskbar and not the Start Button, with click of a hotkey shortcut. Simply download and run the app.

Don't like the Windows 11 taskbar? There are some tweaks you can make to remove some of the annoying bits, and to bring back some of the features from the Windows 10 version.