An oak toy box flatpack can be made at a workbench (steel framed bench or better) in the workshop of a player-owned house. Like when making the normal Oak toy box, this requires 50 Construction, uses 2 oak planks, and gives 120 experience. The flatpack can then be used on a toy box 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 an oak toy box flatpack from scratch gives a profit of: -703
After completing the hard Fremennik achievements, they can also be traded to Advisor Ghrim in exchange for 56 coins being added to your kingdom's coffers in Miscellania. See Flatpack: Miscellania reselling for details.
See Toy box for a list of armours that can be stored.