Food Storage can be found on Home Island, and will always remain there. Complete the "Make some animal feed" and "Feed sheep" quests to unlock it.
Upgrading your Food Storage will increase the number of slots you have for storage of all items.
It can be upgraded 9 times throughout the game, with each upgrade requiring a different set of items.
For more info on upgrading your Food 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!