At http://www.losangeles.cl/comunidad/historia/bandera.htm it is said that the flag was created by 16 year old Santiago Patricio Castro Rojas, winner of a design competition held in April 1975. The flag was approved the following month by communal decree of Mayor Mario R甐s Santander. (The flag designer died suddenly at the age of 20; the flag he created is visible on his tombstone.) The flag is Spanish style triband of green, white, and green, though the text at http://www.losangeles.cl/comunidad/historia/bandera.htm doesn't specify precisely the relative width of the middle stripe — it's just "wider" ("m嫳 ancha") than the others. The ratio is not mentioned, but the image on line is roughly 2:3. The coat of arms is set on the middle of the white stripe, its height slightly larger than 1/3rd of the flag's height. Ant鏮io Martins, 5 December 2002
Coat of arms detail
image by Ant鏮io Martins, 5 December 2002
Arms: Argent, an ox gules between two bars wavy azure, each charged with two barrulets wavy argent, in chief three lightning flashes gules crossed, one in fess and two per saltire; the whole within a border azure charged with eight eagles displayed argent. (The birds could also be called eaglets, since they're so small.) Mike Oettle, 6 December 2002
The meaning of these arms is as follows:
the ox stands for the boldness of the ancient settlers of Laja island
the wavy bars stand for the rivers Biob甐 and Laja, which flow nearby
the lightning flashes stand for the local hydroelectrical plants, and
the eagle bordure stands for the Spanish and later Chilean garrisons at the Biob甐 Line, once the southern border of Chile.