This piece is in plain view and within easy reach.

The trick is just finding where the rope is.

This takes lots of exploring.

Have you looked at the fort?

Herman Toothrot (the bearded old man) may have told you where it is.

In your third encounter with him, if you brush him off, he says he lives in the fort on the volcano.

To get there, from the map screen that includes the south shore, go west to the next map screen.

Near the top of the crater is a fort.

Inside the fort is the first piece of rope.