Boar Island is nicknamed after the many Boars on the island. It is the island directly left of the main island. There are boars on the main island, but most spawn here. It can be reached by Raft or Boat.
To go to Boar Forest, walk into the bush in the middle of the island. Then, you will be transported to an area with Palm trees and some beach. Dig up one of the rocks to get FRP. Walk to the northern border and this is where most of the Boars spawn.