You should prepare some tools in advance. You will need a digging tool such as a pointed stick or shovel, and a pounding tool such as a rounded rock that fits in your hand or a large hammer. You will also need a more or less flat surface to work on, a pointed twig, some kind of scraper (shell, bone, wood, piece of sheet metal, lid from a snuff can), and a way to fire the pottery (many options from hole in the ground to a complex naborigama kiln). If you want a shiny polish, you will also need a stainless steel spoon, polished rock, or glass marble.
First step after gathering the above tools is to dig your clay. If there isn’t clay in your immediate vicinity, you can find it on river banks. Dig the clay out and carry it to your work area. Crush this up with your stone or hammer so that it is a fine dust. Pick out any rocks or twigs. You should get some gritty sand or crushed broken pottery that is the same size as large sand grains (called grog) and some sifted wood ashes and mix them into the powdered clay. I’d estimate a handful of each should be added to each 4 cups of powdered clay. This prevents stress cracking during the firing phase. Mix very well, then add water. Mix it to a consistency like a tough dough with some stretch to it. It shouldn’t break by rolling it into a snake. If it does break, then it is too dry. If this happens, knead in more water and let it rest for a day covered by plastic or oilcloth. You will learn through practice, the best consistency.
Next you make your pottery. Use the pointed stick to score the edges of 2 pieces of clay that will be joined together, then use a few drops of water between the pieces, and smear it together. It takes a bit of practice, but if the pieces are at least as thick as your thumb, it is very easy. Thinner pieces are harder to join smoothly. If you don’t add the ash and sand or grog, this would be the weak points where your pots break in the fire. The less joining you do the stronger the pottery.
Next you let it dry just until it will not move by being pushed lightly. It should not be totally dry. This is called “leather hard”. You take your scraper and go over the surface scraping off high spots so it is somewhat smooth. Then, if you want to, take the marble or smooth stone and give it a high polish by rubbing. If you have a knife or wood carving tools, you can also lightly carve the surface for decoration. If you did not polish it, you can apply glaze to it. If you want to glaze it naturally instead, the instructions will be in the next phase. Let it dry absolutely.
For the next phase you will be firing your pottery. This is needed to keep it from disintegrating in water, or being very easily broken. If you opt to glaze it, it will also hold water better and be less prone to breaking when used to cook food. To glaze it, you have several options:
Applying an even coat of liquid glaze during the previous step
Salt Glazing
Soda Glazing
Ash Glazing
The latter 3 only work if the clay has a medium to high iron content. Most clay does, other than the pure white clay used for making porcelain, so it shouldn’t be a problem. There are hundreds of methods for firing the clay. The fire pit methods are workable, but you almost always lose at least one item due to uneven heating and low temperature drafts from wind. If you need a higher success rate and better fuel efficiency, you should build a kiln. The two simplest are the bottle kiln and the anagama kiln. In a bottle kiln, you have a fire pit with side access on the bottom, a brick or fired ceramic grate above that for pottery to sit on, and a cylinder of walls above that with access from the top for loading and unloading the pottery. On top of that, you dry stack bricks to form a dome with a hole in the top as a lid. In an anagama kiln, it is a place for the fire that is dug into the ground, the pottery is several inches higher on the flat ground set up on little plaster cubes so it doesn’t touch the cool floor. You can make the plaster bits in an ice cube tray. There is a tunnel running from above the fire pit, along the full length of the pottery area, to a chimney that is head high. I built my last anagama kiln out of cinder blocks and loaded it from the top by removing bricks. You have to warm the pots slowly. You build up the fire very slowly. It should be 2-3 hours before you have a blaze. Once you have a blaze going, you need to hold it for a minimum of 6 hours. If you want an ash glaze, you need to fire it for 8-10 days. If not, then the optimum is 8-10 hours of blazing fire. There should be fire coming out the chimney. When you look into the kiln, if the pottery is glowing orange, you can add salt or baking soda and it will react with the clay to make a glass on the outer surface. Once you are done with the time needed for the firing, you close up all holes in the kiln with bricks and mud and let it sit for several days until it is completely cool. This is tempering. The longer it takes to cool, the less chance of cracking and the less chance of breaking during use. Once it is cool, you can unload it. The pots may still be warm, wait until they are room temp before you wash the ashes and dust off. Once washed, they are ready to use.
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