[Torhal]

Building tables programmatically isn't going to save you anything, IMO. You can do the same thing you were doing with the if checks, but in a more terse manner:

        ADVANCED_INTERFACE_GLOBAL_CONSTANTS = ADVANCED_INTERFACE_GLOBAL_CONSTANTS or {}
        ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS = ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS or {}
        ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS.ADVANCED_USER_INTERFACE = ADVANCED_INTERFACE_GLOBAL_CONSTANTS.STAMPS.ADVANCED_USER_INTERFACE or {}

I omitted the last one because checking if a table is nil then setting it to nil if so makes no sense to me.

EDIT: I meant "isn't going to save you anything in this case" - I've built config tables programmatically in some of my AddOns, because otherwise I'd have a bunch of copy-paste code with slightly different labels.