Find a location for your kiln away from buildings, overhanging trees, shrubs and devoid of grass. Lay a brick base, 3 feet on all sides, for a small-sized raku kiln.
Dry-fit the walls of the kiln, laying a double wall of bricks, each brick ¼ inch apart so there is ventilation for the fire. Leave a 1-foot wide gap in the middle of one wall for loading the firewood. Stop when the walls are around 2 feet high. Place the first metal sheet over the top of the walls, to create the firebox.
Lay a floor of firebricks on top of the metal sheet, then continue building up the walls with regular bricks, this time leaving around 1/8 inch between them. Make the walls a further 1 to 2 feet high, depending on the height of the pottery pieces you want to fire. Rest the second metal sheet on top of the walls.
Fill the metal drum ¾ full with newspaper and kindling, and set next to the brick section of the raku kiln---this is the post-oxidation reduction chamber of the kiln.
Lay a floor of sawdust around 3 inches thick on the bottom of the firebox chamber. Fill the chamber completely with kindling and firewood.
Place your pottery pieces in the top section of the kiln. If there is a lot of room to the sides, line the sides with firebricks to fill up the space a bit. Replace the metal sheet on top, then place firebricks all over the top of the metal sheet.
Start the fire in your firebox and let it burn for a while, adding more firewood as necessary, then carefully block up the door with firebricks. Let it burn for five or six hours, unplugging the door to add more firewood as necessary.
While the kiln is still fire-hot, remove the top metal sheet and bricks---this is going to be extremely hot, so wear your goggles and gloves. Take the lid off the metal drum reduction chamber.
Carefully remove a piece of pottery---it should be almost glowing hot---from the kiln chamber with the kiln tongs, then place it in the metal drum and immediately close the lid. The kindling and newspaper in the drum will spontaneously ignite, and with the lid closed, the fire uses up all the oxygen in the drum quickly, and eventually draws it from within the pottery itself, creating the limitless variations of patterns that raku is famous for.
Spray the reduction chamber (metal drum) with water after around 15 minutes to freeze the patterns on the pottery pieces. Refill the drum with combustible material and repeat with the remaining pottery pieces.