An instruction is not a document
The usual starting point is a line in an email: send us the record, legalised. That line names something the reader may never have held. A stamp, though, is added to a sheet of paper by an office looking at that sheet, so until a specific one exists the job has not begun at all, however firm the deadline attached to it.
This is the gap that quietly eats calendars. People count the certifying stages, plan around them, and then discover that the first thing on the list has its own wait in front of it. Closing that gap early costs very little, and it is what turns a vague instruction into a run that can be tracked.
Where the paper actually comes from
Civil records live with the office that registered them. Leicester Registration Service, at 115 Charles Street, Leicester LE1 1FZ, prints certified copies of births, marriages and deaths registered locally, and what it issues is a fresh official print taken from the entry rather than a duplicate of your own sheet. That is what makes it usable in place of the original.
It also means the paper you keep at home need never travel. A certificate lost in transit is replaced only by going back to the beginning, so the habit of sending a fresh copy removes the one loss on this route that no later stage can repair. That single decision is most of what you need for an apostille for Sierra Leone to become a manageable job instead of a risk.
Then the long road begins
Only once a sheet exists does the certifying half start, and on this corridor it is the longer version. Sierra Leone has not joined the Hague Apostille Convention, so document legalisation for Sierra Leone runs as a chain through more than one desk rather than finishing with a single mark, and consular legalisation closes it.
There is no apostille issued in Leicester for use in Sierra Leone that shortens the chain, and no version of it that a receiving desk reads as a finished file. An apostille for Sierra Leone belongs to a different group of destinations altogether, which is why the road here has more stages in it and why the order of them is fixed.
What can be counted before you start
The British side of the bill is knowable in advance. The FCDO Legalisation Office at PO Box 6255, Milton Keynes MK10 1XX is a government office rather than one of ours, it works by post with no counter for callers, and it lists £45 / document for standard post with £40 / document next-day for registered businesses, counted per sheet.
The consular stage carries no published figure, so the honest budget is one firm number and an allowance beside it. There is no apostille from United Kingdom to Sierra Leone to price into that sum, and the number of sheets you decide on at step zero is what multiplies everything else, which is another reason to settle it before the first copy is ordered.