While Gmail is browser based, and we recommend you use the Chrome browser to access it, you can still create a shortcut to Gmail on your Mac dock or Windows taskbar, which will open Gmail in a standalone browser window when clicked.
To create a shortcut to the Gmail app that will open in a new standalone browser window:
Open Gmail as normal in your Chrome browser
Click on the ellipses in the top-right corner of the screen
Choose More tools, then Create shortcut
Enter a name for the shortcut
Check the box to Open as window
Click on Create
A new Gmail window will open. To make it available to click on in future, right-click over the icon and choose Options, Keep in Dock if you are using a Mac, or Pin to taskbar if you are using Windows.