Before the interview, try to find your favorites, too (so you can mention them if the designer doesn’t). Get details on the project itself and the specific role they played in it. Usually, designers don’t list their actual duties, just the end deliverable. Have them walk you through to see if they were involved in strategy, concepting, execution, etc. Of course, just because something isn’t in their portfolio doesn’t mean they can’t create it. But understanding what they regularly tackle helps you see if they’d be a fit.