Also, Mellow Mushroom sells pizza by the slice… but only during lunch.
Montgomery County is a suburban wasteland. If you want pizza by the slice, you’ll have to get on the Red Line and head into the city. Only cities have the foot traffic density to make that business model profitable. The strip malls with Three Brothers locations are all replacements for a traditional “downtown” in neighborhoods with lots of apartments but no real street plan. Since Western MoGoCo has so many luxury condos and single-family homes, there’s never enough population density for a strip mall, and the land values are too high to make one remotely feasible. I bet one of the places in Bethesda might serve by the slice, though.