Temporary portal out where the trees are and chest of storing the wood on the base portal. Then load up on high stamina foods, be fully rested and pop the elder skill.

Chop trees as described by stvlepore. When the axe is blunt or you have no more room teleport home dump wood in chests / repair then teleport back to trees and keep on chopping.

When exploring without portals pick up any and all wood and stash it in chests marked on map. Later in the game when you have the belt you can revisit and collect wood with portals / ships.