An oak dining table flatpack can be made at a workbench (Oak workbench or better) in the workshop of a player-owned house. This requires 22 Construction, uses 4 oak planks, and gives 240 experience. The flatpack can then be used on the table hotspot in the Dining room while in building mode. This requires no Construction level and gives no experience.
The cost of making and selling an oak dining table flatpack from scratch gives a profit of: -2,216
After completing the hard Fremennik achievements, they can also be traded to Advisor Ghrim in exchange for 112 coins being added to your kingdom's coffers in Miscellania. See Flatpack: Miscellania reselling for details.