”Flagsmen” - I love that phrase, may start using it!
Just for your info, and to help your learning, you will often see the terms CAR and NAR used on this site (and elsewhere). They refer to:
CAR - Club Assistant Referee Someone provided by the club to run the line for, often a sub. They can be helpful (but also a hinderance!) but treat their decisions with a pinch of salt. Some will do a fantastic job, some won’t have a clue what they are doing, and some may actively cheat on their team’s behalf.
NAR - Neutral Assistant Referee. These are qualified referees appointed to the game to work with you. They will be neutral and (usually) a great help. Often, along with the referee, will be called the “team of three”
It may be a while before you get NARs, your refereeing career will begin with CARs. I do recommend that fairly early in your refereeing career (ie first season) you try and get some experience of being a NAR. It’ll help you develop as a referee, prepare you for the day that you first have NARs yourself and working as a team of three adds a whole new dimension to refereein.