How to Craft and Upgrade Backpacks
Starting From Backpack Base 0
Place a Backpack Base 0 in a crafting grid to begin the base line. From there you progress through Backpack Base 2, Backpack Base 3, Backpack Base 4, and Backpack Base 5, each tier built from the previous base. Backpack 6 is the top of the chain and is reached through a smithing_transform recipe rather than a normal crafting_shaped recipe, so you will need a smithing table setup for that final step.
Using the Backpack
Once you have a backpack item, it stores your items and can be opened from your inventory or placed in the world depending on the tier. Higher bases hold more. Keep the previous base on hand when upgrading so you do not have to rebuild from scratch.
Planning Your Upgrades
Work up the base chain in order: Backpack Base 0, then 2, 3, 4, 5, and finally Backpack 6 via smithing. Do not skip tiers, because each recipe consumes the tier below it. Gather the materials for the next base before you start, then craft the upgrade in one sitting so you are not left holding a half-finished line.