You need Leather to craft Backpacks and your Leather Armor Set that includes a Helmet, Body Armor, and Greaves in Raft. This is one crafting material that will require you to go out on a proper hunting expedition.
If you are ready and willing, the following guide will tell you where to go and what to hunt to get Leather in Raft.
How To Get Leather In Raft
Leather is obtained by killing wild animals such as Bears and Warthogs that are not found on small islands as they are unable to host wildlife.
In order to get Leather, you need to locate large islands for which you can use your navigation system. Make use of your Receiver and Antenna and find large islands where you can find Warthogs.
Bears are found only on Balboa Island and the islands nearby within the same biome which is the last location you go to in the first chapter of the story.
After getting to the Balboa island, get off the Raft and while carrying at least three spears. You will have to explore the island and when you come across a bear, hunt it with your spear.
A good technique to hunt a bear is letting him attack you and when it comes close, stab him with the spear. Killing each bear gives you four leather and this is a pretty simple task to do. Besides giving leather, it also gives raw meat and a bear head.
In the same way, you can find a Warthog and then kill it to obtain leather. The easiest way of killing a Warthog is to first bring him near water. Then get near the shore and wait for the Warthog to attack you.
As he proceeds to attack, get into the water and wait for the Warthog to finish charging. As he stops charging, he gets disoriented. This is your moment now. Stab him with your spear and get the job done. Killing Warthog also gives you meat and Warthog head.