There will still be the back room of the union hall with the faithful premarking wads of ballots to be "found" as soon as they know how many they need to steal the election. And the clerical "error" in the count. And the "accidental" delay in the overseas military vote.
The first stage in the counting process in the UK is called ‘verification’. Where every ballot is counted and compared to the number of ballots issued at the polling station. Any major discrepancy leads to an investigation as to why ballots are missing, or how they have miraculously appeared. It’s very rare for a discrepancy to be found.
The verification number is announced publically - so now everybody knows there are - for example - 323,763 ballots being counted in a particular area.
And only after this, do they start actually counting and allocating the ballots to see who people voted for.
And the final count has to match that total number - if you watched the count, you would have seen that in addition to the In and Out numbers, they also had to say how many blank ballots there were, how many had been discounted because a voter could be identified (they’d violated the secret ballot rule), how many people had voted for both options.
The point is the system really doesn’t allow for extra ballots to be ‘found’ in the way you describe. If there were 10,000 more votes at the final tally than there were at verification, it would be obvious.
I have no doubt that in 2000 the dems pulled a bunch of ballots out their orifices which they tried to punch with an awl or nail set. They called Gore and told him to 'unconcede'. However, the punching of the paper ballots was done hastily, hence all the 'hanging chads'.