Simmer fruits and veggies: Roughly chop the fruits and veggies and add to a large pot with the dashi. Bring to a boil, lower to simmer, cover, and simmer for 1 hour. If using kombu, remove after 20 minutes of gentle simmering, or sooner if you notice it starting to melt into the sauce.
Add spices and simmer: Stir in the spices and simmer for another hour.
Blend: Turn off the heat and remove the cinnamon stick and bay leaves. Use an immersion blender to blend everything together, or transfer to a blender in batches. Be careful not to over-blend -- you don't want a super smooth mixture -- or you won't be able to strain out the pulp effectively.
Strain: You want to use a very fine mesh strainer to remove as much of the pulp as possible (this will result in a very smooth sauce with a longer shelf life). I recommend using a nut milk bag if possible, but be aware that it will stain your nut milk bag orange/red. Let the mixture cool first until cool enough to handle since you will be using your hands to squeeze out the liquid. (Save the pulp! It's full of fruit and veggie puree and flavor from the spices, great in stews and curries.)
Add seasonings: Add the strained liquid back to the pot and stir in the seasonings. Bring to a simmer and cook for 30 minutes.
Add thickener (optional): For a thicker sauce, mix flour with some cold water (just enough to dissolve the flour) until smooth and no lumps remain. In the last 10 minutes of simmering, add in the flour mixture. Stir frequently until sauce thickens. (Add more flour, one tablespoon at a time, if you would like a thicker sauce.)
Cool and Store: If you notice small clumps of flour in your sauce, strain it again before storing. You can just pour it through a fine mesh strainer or sieve. Let cool completely, then transfer to bottles or jars, seal, and store in the fridge for 1-2 months.