Generally, I take myself off to a location that is not my office for the duration of my hour - mostly I go grab a sandwich (because I like tuna sandwiches, but do not like them soggy, which is what they are if they sit in a lunch bag for 5 or 6 hours - and the whole bringing enough random crap to build a tuna sandwich on-site is a giant pain in the butt to save me three dollars).
I have learned through bitter and repeated experience that if I do not physically leave my office building, I will not get a lunch break at all. What I will get is interrupted every two to three minutes with “Oh, are you on your lunch? Would you mind doing this real quick? Then you can go back to lunch!” This happens even if I am not at my desk, but am instead in, for example, the breakroom (not that my current office possesses such an amenity - we have a refrigerator that shares a room with the main printer/copier for the office). No, it does not matter that I take my lunch at the same time every single day - the interruptions inevitably start at around 12:10 - just long enough for me to extract lunch from a bag, get settled, and open my book. I have noted that these “emergency” tasks can always seem to wait if my attorneys can’t physically locate me to ask me - they never, ever ask any of the other assistants to do it (which they damn well would if it were a real emergency). Accordingly, I have learned it’s best if I just make myself scarce for that hour.