I don’t believe there is currently a way to do it without a shortcut/snippet plugin.
The only command I’m aware of is “Toggle code” which only toggles single-line code, not multi-line blocks.
Could make a nice feature request. Or discuss in this thread: Meta Post - Hotkeys
(Interestingly enough, if you select a block of text, including a line above and below, and run that command 3 times (say, with a hotkey assigned), you end up with a triple-tick code block, minus the language definition.)