Collect hard firebrick (red bricks), an ideal material to build a homemade kiln. These bricks are made of clay. Brick-made pottery kilns can withstand heat, absorb it and transfer it back to the pots so that they are heated uniformly and for long periods of time. For the fire, get dry seasoned wood that can burn at a very high temperature. Use a newspaper to help start the wood fire.
Make a dry-stacked kiln by stacking the bricks one on top of the other without using mortar--the kiln will be temporary, but it will still achieve more or less the same temperature as a kiln made using mortar. The dry-stacked kiln is made by placing the the firebox (where the wood is kept) below and the ware chamber (where pots are placed) above it.
Put the pots inside the ware chamber, and stack more bricks at the top to create a roof. Build a brick chimney or make a hole at one end, so that you can insert a pipe into the hole. This will draw the heat and smoke through the fireplace and away from the kiln for uniform and effective heating.
Make a small fire to fire up the kiln. Don't heat it too fast because the clay will crack. It will take about two hours or more to feed the fire and increase the heat slowly so that you can have a better finished product.