You can portal to the swamp area, build a safe spot to put your smelter and get 6 copper from a nearby black forest make a forge and then smelt 10 iron to turn into 100 nails at the forge and grab the extra materials for the longboat (most recyclable from karve) once built Now you'll only have to make one return trip back to home with a boat full to the brim of ore.

To answer your question though, you probably wouldn't have figured that out on your first playthrough. I have my own horror story regarding this matter. I spose you would have figured out once you did a trip back you can make the longboat and then would been oh damn now I can transport heaps of ore no problem and then later realising the logistical time savings you could have made.