[lawtalkinghuman]

Same in the UK.

Votes close at 10pm. Might be a few stragglers left in the queue, so call it 10:15pm. (Exit poll results are embargoed until 10pm.)

Ballot boxes are transferred from individual polling station to the location of the count. The postal votes have been pre-checked (but the actual ballot envelope has not been opened or counted) and are there to be counted alongside the ballots from the polling stations.

Then a small army of vote counters go through the ballots and count them and stack together ballots by vote. There are observers - both independent and appointed by the candidates. The returning officer counts the batches up, adjudicates any unclear or challenged ballot, then declares the result.

The early results come out usually about 1 or 2. The bulk of the results come out about 4 or 5. Some constituencies might take a bit longer - it's a lot less effort to get ballot boxes a mile or two down the road in a city centre constituency than getting them from Scottish islands etc. - but it'll be clear who has the majority by 6 or 7 the next day.

I can appreciate that the US is significantly larger than the UK, but pencil-and-paper voting with prompt manual counts is eminently possible.