The job ends; the paper does not
Almost every guide stops at the last stamp, as if the paper vanishes once it is complete. It does not. A finished sheet gets handed to somebody, filed, asked for again, and sometimes needed a second time years later. Deciding in advance where each copy ends up is the difference between doing this once and doing it twice.
The route Guinea uses, and what it consumes
Guinea has not joined the Hague Apostille Convention, so document legalisation for Guinea runs through consular channels rather than ending at the British stage. That matters for planning because a longer chain has more desks in it, and desks that process paper tend to keep it. A route with two endings eats more copies than a route with one.
There is no such finished item as an apostille issued in Birmingham for use in Guinea, so do not budget for one sheet and hope. Budget for the number of permanent holders your file will have, and treat each finished paper as something that will leave your hands for good.
Who keeps which sheet
Work backwards from the far end. Someone in Guinea has asked for this paper and will keep what they are given. The consular desk that closes the file handles a copy on its way through. You want one complete sheet that stays with you, because it is the only proof of what the finished article looked like.
That is usually three, not one, and people discover it at the worst moment. The whole point of ordering the set on the same day is that all the copies then match: same wording, same date, same officer, one consistent story wherever they turn up.
Keeping a finished paper usable
Once a certificate is attached, the pair is a single item and must stay whole. Keep it flat, keep it out of a laminator, and keep it in one place with the rest of the set. A scan made before anything is handed over gives you a reference for what existed, which is useful when someone later asks what was issued.
The safety net is the register office. Birmingham Register Office at Holliday Street issues certified copies of civil records, so a lost or damaged set can be rebuilt from the source rather than reconstructed from memory. That is a good reason never to let the record you keep at home enter the chain in the first place.