A mahogany armour case flatpack can be made at a workbench (Bench with lathe only) in the workshop of a player-owned house. Like when making the normal Mahogany armour case, this requires 82 Construction, uses 3 mahogany planks, and gives 420 experience. The flatpack can then be used on a armour case hotspot in a Costume room, either in building mode or not. This requires no Construction level and gives no experience.
The cost of making and selling a mahogany armour case flatpack from scratch gives a profit of: -3,434
After completing the hard Fremennik achievements, they can also be traded to Advisor Ghrim in exchange for 507 coins being added to your kingdom's coffers in Miscellania. See Flatpack: Miscellania reselling for details.
See Armour case for a list of armours that can be stored.