Sitting at the BOS global entry "waiting area" now for a walk-in. There's just three chairs in a small hallway outside the secured area of terminal E. You sit outside a secure door waiting for someone to pop out and call a name. It seems like that's your only chance to talk with anyone. You just have to sit and hope someone doesn't show up so you can take their spot.

There's three of us waiting for a walk-in now. Friday afternoon on Memorial Day weekend was probably not the best choice. One guy who was waiting for his appointment said mornings might be best. He tried to walk in as well and failed but ended up finding a closer appointment time after checking a bit. I'm probably going to give up after waiting for over an hour.