Hesjing means to create long temporary fence-like structures and then lifting the gross onto it.
If done correctly so the water can easily run off it can then survive a rainfall or two unlike what happens if you dry it flat.
This was actually important ant least in costal climates back before motorized fans made drying it indoors an alternative.
(Brings me back, woke up from the huge fan many days in the summer holiday. I also remember learning to start it, there was a delta/y switcher on it but I have now forgotten which configuration was for spinning it up and which was for steady state.)
Wikimedia seems to have a list of haystack images by country at https://commons.wikimedia.org/wiki/Category:Haystacks_by_cou... and what do you know, Swiss actually do it differently! Building around a central pole, rather than a more elaborate frame https://commons.wikimedia.org/wiki/Category:Haystacks_in_Swi...
Probably. Guess I'm not old enough to have ever witnessed manual baling then! That's a TIL for me :)
More importantly, a bale won't stay dry inside if it's rained on. So you need to store them in barns.