A mahogany bench flatpack can be made at a workbench (Steel framed bench or better) in the Workshop of a Player-owned house. This requires 52 Construction, uses 4 mahogany planks, and gives 560 experience. The flatpack can then be used on a seating space hotspot in a Dining room or Throne room, while in building mode. This requires no Construction level and gives no experience.
The cost of making and selling a mahogany bench flatpack from scratch gives a profit of: -5,550
After completing the hard Fremennik achievements, they can also be traded to Advisor Ghrim in exchange for 675 coins being added to your kingdom's coffers in Miscellania. See Flatpack: Miscellania reselling for details.