I needed some cordage for a project so I harvested some Larch (Larix kaempferi) roots. It is easiest to get them from mossy ground as the roots grow long and striaght and are easy to extract.
Spruce roots are also good amongst many others.
You scrape back the soil or moss and find a good root about little finger thick. Then you trace it through the ground until you have the length you desire. Cut the root neatly with a sharp knife so it has a chance to seal.
The root is closer to wire than rope in properties but are generally strong and flexible..
At this point the outer bark can be removed and the root can be dried if the root is to be used in the future. I wanted the root for immediate rough work so i didnt bother romoving the bark but did a bit for illustration purposes.
To make the bark easier to remove you can make a tool like this.The excess can be removed by washing in water. They will be creamy white and smell of resin. The bark is much easier to remove during spring and summer due to the sap flowing.
You can then split the root into halves or quarters. Which is quite simple if done slowly and practised.
A cut is made in the end of the root and it is split down the centre. You need to practice. Is it runs off you need to apply more pressure on the thicker side.