Click the three vertical dots in the right-hand corner -> go to More tools -> and then Create shortcut.
Make sure that "Open as window" is checked.
Right-click or alt+click on the Gmail icon in the dock, go to Options, and then Keep in Dock. (windows right click on the icon on the taskbar and pin to taskbar)
(Mac) Or drag the Gmail icon onto your desktop. The icon is located in your chrome apps folder. This folder should have popped up upon creating the shortcut.
