A DIY stake anvil, in the fashion of early iron age anvils.
A stake anvil is one of the oldest styles of iron anvil out there, they have been used to good effect since the Mid-Iron Age, well over 1,800 years, and was the most common portable anvil in Medieval times, being pointed on the lower end to be driven into a stump so the combined mass off stake anvil and wooden stump will absorb blows allowing you to make items up to a medium-size knife. Since it is assumed, at this point, that you do not have access to an anvil, let's discuss ways you can accomplish an improvised surface to create this project. What you will be doing is called "upsetting" the metal to form the working surace of the anvil, which is striking the top, imagine you are hitting an oversized, red-hot nail, the head will deform, spreading the hot metal out, and back down on itsel, enlarging the surface area, and shortening the length of thee piece. To practice for a larger stake anvil, I suggest you initially practice this with a railroad spike (I don't use railroad spikes as knives, the quality of the steel is too poor, and the amount of carbon isn't high enough to hold an edge), seek out a nice looking spike which is not too rusty, deformed, and has a "C" as one of the letters on the head, this indicates it is a carbon-steel railroad spike.
Examine the picture of the spike in the picture, it has been driven into the end-grain (round end) o a log at a height at which you will work, if you are not aware at what height your anvil surface should be at, a common modern height is your knuckles if you make a fist and have your arm at your side when standing. Medieval Smiths (and before) actually worked at the stake anvil on their knees, since they usually worked with a forge dug into the ground and lined with clay. A word about the forge heat you will need, and that is medium-high, about 1,700 to 2,000 degrees Fahrenheight, perhaps more, so this is NOT something you can do easily with just a torch, you will need to build or find a forge, either gas, coal, or charcoal (Please see my article about these fuels).
Once you have your height estimated, you drive the spike into the end of the log,but not too deeply, because you must heat it up in the forge to upset it. Note the bent piece of metal used to allow you to "wedge" the spike in, allowing you to remove it. Once you have a square hole created in the log ( heavy, hardwood logs are necessary!!) you can begin to heat the HEAD of the spike, recall you are upsetting the head, and do not need the heat more than a half inch belowthe head, or when you begin to hit it, it will bend, rather than upset. Once the heat is a bright orange, replace the spike in the log, along with the wedge, and begin hitting the head , concentrating the blows so that you strike the area above the metal shank, don't strike too hard over the unsupported area, as it will bend the spike. Chances are, you will only get three to five blows in before the spike will stop upsetting, so re-heat and repeat these steps until the head has enlarged and flattened sufficently to provide you a decent working surface, possibly as much as 8-12 heats, so be patient, this is a slow process, you are moving a lot of metal. When you have the head spread, flattened and slightly rounded, you may move on the the next step, which is to normalize the working surface, heating it to a bright orange, without burning, and then allowing the head to cool completely to black, repeat three times. Often, in tool-making, once the third normalizing is done up to non-magnetic heat (1,650 degrees F.) it would be quenched in oil, if you wish to do this, and I don't suggest it initially, since you will be polishing this face and using it ONLY to forge metals at a red-hot heat, since a decent anvil is NEVER used to form cold metal, except sheet metal, then this stake anvil will work-harden adequately, but if you do notice it getting dents in it in normal use, repolish it and heat to non-magnetic, then quench in oil briefly to a depth of no more than two inches. Once cooled, file, clean and polish the surface with progressive grits of sandpaper to a mirror finish.
The resultant stake is a good one for practice or beginning, and will allow you to gain the experience to work on a larger stake, which will require a larger steel rod, what I have had exceptional good luck with is a broken jackhammer tool of about 1 3/4" diameter up to 2", what you will also need to do this larger project is a steel plate of at least 3" thickness, and then sufficient help from assistants to drop-hammer the piece onto the plate, meaning hold the cold end up, and drop the hot end onto the 3" thick plate until it is adequately upset, then drive the stake into the ground with the hot end up and have assistants support it while you strike it with a hammer while red hot to level and planish (smooth) the surface until you ar happy it is level and usable. Jackhammer bit steel is tough, high quality tool steel which will work harden with use, but I would recommend that you harden the surfaceto 3" by oil-quenching at non-magnetic temperature, but not holding the steel in the oil for more than 20-25 seconds. The steel is already tough and very hard, and you don't want it too hard. The oil I use is extra-virgin olive oil, because, quite ankly, it smells better than motor oil, and I do a lot of knives, so the consistency I get with olive oil is better.