To make a liter or so of chicken stock:
1 "stew chicken" or 2-3 pounds chicken parts (feet, and legs or thighs) go into a pot with 4 liters water. Bring to a boil, reduce to simmer, and skim off scum til mostly clear (20 minutes or so).
Add a bunch of green onions. Simmer covered as low as you can until stock is to approximately desired richness and chicken is extracted and falling apart. You will have 1-1.5 liters of stock; reduce further after removing chicken if necessary.
Stock can be cooled and frozen from here, or made straight into a soup.