Choose your piece of bamboo. Inspect closely for cracks. Keep in mind the length of the bamboo affects the tone of the instrument. Longer tubes produce a deeper sound.
Close one end of the bamboo by inserting the section of wooden dowel into the end. Sand as needed to ensure a snug fit. Secure dowel in place by spreading wood glue on its diameter.
Sand the bamboo, rubbing with the grain. Continue until bamboo is smooth. Round the outer edges by spinning the ends on sandpaper at a 45-degree angle.
Place a piece of sandpaper on a flat surface. Position the sealed end of the flute at a 45-degree angle to the sandpaper. Taking care not to roll the flute, sand a flat wedge approximately 1-inch long. This will be the position of the nose hole. The flattened spot increases air flow as you exhale air over the hole.
Wrap the wedged section with masking tape. The tape minimizes the chance of cracking the bamboo when drilling. Mark the drilling location in the center of the wedge and just below the dowel insert.
Wrap the center 4-inch section of the flute with masking tape. Approximate the center of the flute. Mark your center finger hole in alignment with the nose hole. Mark a second hole 1-inch above the center and a third 1-inch below the center mark.
Drill the holes with an 8 mm drill bit. Remove masking tape.
Insert the narrow wood file into the nose hole. File the lower edge of the hole to thin the bamboo wall. The thinner wall will increase the air flow through the flute. Sand any rough edges caused by the drilling.