Big Storage can be found on Home Island. It will unlock at level 8 when you complete the "Get Big Storage" quest.
Upgrading your Big Storage will increase the number of slots you have for storage of all items.
It can be upgraded 19 times throughout the game, with each upgrade requiring a different set of items.
For more information on upgrading your Big Storage, check the guides we have posted to our official Facebook group and Discord channel.
To learn more about building, check out the Crafting Stations section!