Well the way to set slots from buttons would be something like this:
utter_ask_SLOT_NAME:
- text: "Please choose one."
buttons:
- title: "AL"
payload: '/inform{"PERMANENTADDRESSSTATE": "Alaska"}'
- title: "AZ"
payload: '/inform{"PERMANENTADDRESSSTATE": "Arizona"}'
...
And if you wanted to set buttons within a custom action or validation action check out the solution here: Buttons without text