Level 5 Referee
As per law 3, competition rules are entitled to (and in my experience, almost always do) ask that only named players and substitutes may be involved, so the "blank paper" solution isn't a panacea. Particularly for a cup final, there are likely to be some eligibility requirements around players having been involved in earlier rounds, so you can't just stand at the half way line and allow any subs without knowing their names.Blank paper, number off, number on, each and every sub
you now have an accurate note of who is n the pitch at the end.
At the end, players can come and go as they wish, toilet if they so desire.
must be regional because I have never used, nor seen said practice. Its certainly not a command you can issue, nor one you can sanction if not adhered to
If named substitutes are a requirement then you would need to check player names when they are to be substituted on, and if return subs are allowed then you would need a list of not just the substitutes, but also the names of any starting player that have come off. Blank piece of paper with a bunch of numbers written on is not enough.