Heat
oil in large stockpot over medium–high heat until shimmering; add
onion, celery and carrots and cook until slightly softened, 3 to 5 minutes.
Transfer vegetables to large bowl. Brown chicken in two batches, cooking on
each side until lightly browned, about 5 minutes per side; transfer to bowl
with vegetables. Return vegetables and chicken to pot. Reduce heat to low,
cover, and sweat until chicken releases its juices, about 20 minutes.
Increase heat to high; add boiling water, salt, and bay leaves. Bring to
boil, then reduce heat to low; cover and simmer slowly until stock is rich
and flavorful, about 20 —
30 minutes,
skimming foam off surface, if desired.

Strain
broth and discard solids. Before using, defat stock. After stock has been
refrigerated, the fat hardens on the surface and is very easy to remove with
a spoon.

To defat hot stock, use a ladle or fat separator.