I recommend you search the Forum for “offboarding” and I think you’ll find a couple of topics/posts.
Also, you might find my earlier Forum Leaders tips of value related to this:
And looking at “onboarding” would give you ideas too, even if it’s the opposite! There’s also an Asana-provided project template: “Asana Employee Onboarding” that you’ll find in orange + Create > Project > From Template.