After seeing another girl's panties on the bathroom floor, Flo are done with their man. They stuff his belongings in the titular cardboard box and change their number and the locks. "'Cardboard Box' is one of the first songs we wrote as a group and during the process we opened up about relationship struggles and experiences of moving on from an ex," Flo told Official Charts
. "It was a special bonding moment and feels fitting that it's our debut single."