Apple - How do you extend the time required to trigger hot corner actions?

I do not know how do delay the triggering, but you can add modifier keys to the hot corners in order to avoid accidental activation:

Hold down ⌘,⌥,⇧ or ctrl while selecting an option from the list.

a bit late, but I guess relevant...

I was stuck with the same issue of adding a delay, NOT a modifier key.

Well, there's a workaround.

In the corner you want to use as a lock after a short delay, put Start Screen Saver in the Hot Corners dialogue, instead of Lock Screen. Then go to Security & Privacy and under General, set 5 seconds delay in Require Password after...

And you're done!