I just watched a 26 minute video from Blender Guru marking seams on an Anvil. Except the whole seaming went right over my head and I don’t think I learned anything. How does one know where to seam???
I guess the easiest way to think about it is if you wanted to flatten the object out onto one or more pieces of paper - where would you place the cuts?
Kinda the reverse of this video
If you think of a simple example like a dice - if you wanted to flatten the dice out onto a piece of paper - you’d have to cut along some of the edges in order to be able to fold it out. This is what it would look like after making the cuts.
Wherever you would make a physical cut like this - that’s where your seam goes. Of course you could cut along all edges and completely separate all of the faces of the dice - whether you do that is up to you and all you would have to do is create additional seams along the folds.
On more complex or curved geometry - like the horn end of the anvil, where you place a seam is often an artistic judgement call (as it is in Andrew’s video). He chose to place it on the underside I believe - since the seam will probably be somewhat visible. He chose to place the seam on an area of the object that would be mostly out of view.
Also, quite frankly, “projection painting” sometimes offers a much-more-agreeable approach: you “spray-paint,” as it were, the necessary texture-image on all sides of the object(s), which have been mapped automatically (because it no longer matters …).