Heat your oil in a large pot, then fry the onion until partly translucent.
Add the garlic, ginger and curry powder and fry for about a minute for the spices and aromatics to release their flavor.
Add chicken, 2 cups of water and 2 cups of coconut milk. Bring to a boil then lower to a simmer and cover. Simmer for 20 minutes or until very soft.
Add vegetables and bring to a boil again. Turn down heat and cover again. Simmer for 20 minutes or until soft.
Mix the 6 Tb flour with the 6 Tb water until it's smooth (and an extra tablespoon or so of curry if you like). Then add this slurry straight into the pot. Turn the heat up to medium and stir until thickened.