At their simplest, forges contain two components: a burner to produce heat and a vessel or box to contain the heat. Some possible construction types include using pre-made cement blocks; a stainless steel sink and stove pipe; or poured cement with brass or steel piping. Fuel sources include propane and coal.
For a basic Oriental trough forge design, lay cement blocks or bricks in an alternating pattern to form a base and two parallel walls, leaving an opening on each and a brick-wide opening on one wall to force air through. A shop vac makes a successful bellows in this case, keeping air circulating to fuel the heat source. Burn coal on the base to heat the forge.
For a recycling do-it-yourself version, use a stainless steel sink for the body of the forge, lining one basin of the sink with cement to incorporate the heat source and using the other basin for a reservoir to cool the heated metal. For ventilation, partially cover the forge section of the sink with sheet metal funneling into a stove pipe, and use the sink drain to blast air into the forge as the bellows.
As an variation on the cement block design, create a frame using metal piping and poured cement. Utilizing a metal pipe feeding into the body of the forge, pipe in heat using a propane reducer as the heat source.