Once you reach the 5000 max materials, get 3 friends, hop in an early storm shield mission and build until you guys drop. It takes a while but it’s the best way to do it.
Warning! If you leave or lose connection during the mission, you will lose progress made in said mission. Make sure you finish the mission and see the results screen to ensure progression.
Edit: as long as you don’t start the mission yet, every build is one hit with a pickaxe to make building easier. Once you run out of mats, destroy the base.
Also, do not build over the soccer field when playing at Stonewood Storm Shield. It will cause the builds to stay and will keep your builds. It is hard to break it, so try to make a warning wall to not go past.