Be sure to carefully examine each photo and read the highlights, the majority of this instructable is explained and documented in photos. Any and all questions will be answered to the best of the ability, and if we don't know we'll do our best to find out.
This forge is a bit more durable, but much less portable than other models you may have seen, but it can also melt steel should you choose to buy a proper clay-graphite crucible. The ability to melt steel is given to the furnace by adding clay/brick walls to the top of the furnace as seen in step three, no extra equipment (aside from the mud/brick and crucible) is needed.
Step 1: Materials
2" Steel nipple
2" Steel end cap
Charcoal starter fluid
PCV pipe segment (~1.5" diameter)
Slag stick (A long bolt will work)
Proper safety equipment (eye protection, welding gloves, etc.)
Step 2: Construction of the furnace
First, dig a small depression to sit the charcoal starter in, using the mud cover up all but one of the holes in the bottom. Fill the starter approx. 1/2 way with the charcoal. Take the blow dryer and duct tape a length of PVC pipe to it. Stick the end of the PVC in the one remaining hole and set the blow dryer on a brick or something else to keep it directly off the ground. Center the crucible (more on that later) in the furnace and fill in the sides of the furnace around the crucible with more charcoal. Soak with starter fluid and light a match.
We tried using a clay flowerpot but it cracked minutes into the first burn of the furnace. Not 100% on what happened there, either the pot wasn't completely clay, it wasn't properly fired, etc.