An oak bed 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 bed, this requires 30 Construction, uses 3 oak planks, 2 bolts of cloth, and gives 210 experience. The flatpack can then be used on a bed 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 bed flatpack from scratch gives a profit of: -2,505
After completing the hard Fremennik achievements, hey can also be traded to Advisor Ghrim in exchange for 230 coins being added to your kingdom's coffers in Miscellania. See Flatpack: Miscellania reselling for details.