Turn the barrel upside down and empty any remaining wood or solid residue.
Pour water into the barrel and place the barrel in the sun. Allow the water to evaporate for up to one week. If any water remains after a week, turn the barrel upside down and allow it to drain for 24 hours.
Remove the bottom of the barrel using a saw. Pull the metal staves off the barrel. These staves should detach from the barrel without the need of additional tools. Use the saw to cut a large piece out of the top portion of the barrel to make a square back piece. This back piece should be about two-feet by two-feet.
Cut the bottom of the barrel into strips. Cut the remaining portion of the barrel into strips. These strips should be roughly three-feet by six-inches. Place two of these strips across the square back, at the top and bottom of the back. Attach these strips to the back using nails. Insert the nails into the back piece so that the sharp end of the nails extends through the strips.
Nail a piece of wood to the back, extending towards the ground. This will be a leg and it should protrude two to three inches from the barrel. Nail another, equally-sized piece of wood on the other side of the back for the other leg.
Affix the seat to the back rest. Make a seat by placing two or three slats of wood perpendicular to the back rest, at the bottom. Nail these slats to the back rest by inserting nails at a 45 degree angle.
Nail arm rests to the seat. Place one plank of wood, about 8 to 12 inches long, against the back rest. This plank should hit the middle of the back rest and should be perpendicular to the back rest. The flat side of this plank is parallel to the ground. Nail this plank to the back rest. Nail another plank on the other side of the back rest.
Sand the chair using a medium-grit sandpaper. Spray a wood varnish on the chair and allow it to dry for 4 hours.