Typically, elsewhere in the ancient world, big ships were the specialty of small outfits, basically one family or extended family, and they didn’t work from blueprints. Ships were built to size, but the needed materials (the wood had to be long enough and sound enough) had to be available. The whole group would work on it, everyone doing the same steps at the same time for the more repetitive tasks, under a small hierarchy of experienced builders.
When Alexander the Great decided to return to Persia from India, he ordered ships built on the Indus sufficient to carry his whole force, and the task was accomplished in six months — other than the fact that part of the force had to march along either side of the river due to insufficient space. Big Al’s plan was to deal with any attacks by coordinated responses on land and water, oh, and to sack anything that slammed the door in his face. On the way downriver, some ships may have been lost due to running aground and sinking, or were lost in battle.
He often fought against numerical superiority, but by the time his army basically voted against further conquest to the east, his army had probably reached one of its peaks, perhaps 150,000, plus the entourage of acquired wives and children. The largest force he ever had available was during his campaign in central Asia, HQed in Balkh — roughly 300,000 men, perhaps more, most of which had arrived during the winter in response to his call-ups.
Thank you for that information,