An oak wardrobe flatpack can be made at a workbench (Oak workbench or better) in the workshop of a player-owned house. Like when making the normal Oak wardrobe, this requires 39 Construction, uses 3 oak planks, and gives 180 experience. The flatpack can then be used on a wardrobe hotspot in a Bedroom, either in building mode or not. This requires no Construction level and gives no experience.
The cost of making and selling an oak wardrobe flatpack from scratch gives a profit of: -1,540
After completing the hard Fremennik Tasks, they can also be traded to Advisor Ghrim in exchange for 84 coins being added to your kingdom's coffers in Miscellania. See Flatpack: Miscellania reselling for details.