A mahogany armchair flatpack can be made at a workbench (Steel framed bench or better) in the workshop of a player-owned house. This requires 50 Construction, uses 2 mahogany planks, and gives 280 experience. The flatpack can then be used on the chair space hotspot in the parlour, while in building mode. This requires no Construction level and gives no experience.
The cost of making and selling a mahogany armchair flatpack from scratch gives a profit of: -2,524
After completing the hard Fremennik achievements, they can also be traded to Advisor Ghrim in exchange for 113 coins being added to your kingdom's coffers in Miscellania. See Flatpack: Miscellania reselling for details.