How to absorb/remove excess water that you've added to a dish?

Another solution if you dont have any thickeners on hand is to strain the 'soup' using a fine wire mesh sieve, then boil off the excess fluid stirring frequently until its the consistency/volume you want, then recombine.

Depending on what you're cooking this may destroy the flavour in the sauce, though in my experience this does not happen often.

Depending on how much water you have left over I might do one or more of the following:

1. Toss in quinoa (GF ancient grain, 10m cooking time, estimate the same water:grain ratio as rice)

2. Bulgur wheat/couscous (gluten-y, and will absorb lots of water without needing much cooking time at all...too much and it get's mushy fast)

3. TPV (texturized vegetable protein, may or may not be comprised totally of vital wheat gluten or soy protein, doesn't really need much heating, it absorbs water like a champ)

4. Dehydrated onions, carrots, or celery if they don't interfere with the flavor profile

5. If there is an INORDINATE amount of water, I will just give up and decide it's now a soup...I will incorporate one of the previous grain additions and pitch in some egg whites(think like egg-drop soup, drizzling egg whites slowly into the warm water to get coagulation)

6. If you don't like cornstarch... xanthan gum or arrowroot may also be useful in small quantities for thickening. Some people have reported a bitter taste using these in large quantities, so be aware.

Hope these were helpful.

This sounds just like my cooking technique, and I have come up with a few ways to recover from overwatering.

Always lowball the amount of water

Like you said, you can always add water later. But if you're not watching the dish, you don't want the water to run out and burn.

Corn starch

Corn starch is a good way to thicken up the water into something more saucy. This is my preferred method if the extra water actually has flavor, because it adds a nice sauciness to the dish. Make a corn starch 'slurry' by mixing cold water and some corn starch, then add that to the hot dish that still cooking. You want to cook the dish for a few minutes after adding corn starch to let it thicken and cook out the raw flour flavor. You'll have to adjust the amount of corn starch depending on how much water there is, but a little goes a long way, its WAY more absorbent than flour.

Remove the lid and stir occasionally

This is the easy way, but it takes a while and sometime you can cook your dish in to mush. This lets excess water evaporate, and stirring just helps that a little.

Stuff happens to us all, especially when using highly scientific methods. If your seasonings/flavors are the way you want them and the only issue is too much liquid, just ladle out until you are left with amount of liquid you want.

You can even save the seasoned liquid you take out (stored in refrigerator) and use it later when preparing another dish.

Your highly technical method, being what it is, provides its own solution to too much water. Just let it simmer a few more minutes with no lid. That's it. The flavors will intensify as the liquids reduce. Keep it right at that point between a simmer and a boil, it won't take long at all.