The BSA Handbook says,
“A national flag that is worn beyond repair may be burned in a fire. The ceremony should be conducted with dignity and respect and the flag burned completely to ashes.”
Being aware of the material from which your flag is made will drive your method of retirement. Unlike the cotton and wool flags made in the early 20th century, some modern flags are made out of synthetic materials like nylon. Burning nylon is not recommended but it can be recycled to become a new flag again.
The traditional method of retirement is to incinerate a cotton flag, but this does not mean that one should simply drop the whole flag into a fire.
A flag ceases to be a flag when it is cut into pieces. In addition, smaller pieces are easier to completely incinerate. First cut the flag in half, vertically, leaving the blue star field whole. Then, place the two halves together and cut them in half, horizontally.
While the Scouts are performing the flag dissection, other Scouts should start and tend a medium size, wood fire. The Scouts maintain a vigil over the fire until all traces of the flag remnants are destroyed. The fire is then extinguished and the ashes are buried. The burial can be completed with a moment of silence while taps is played by a bugler.