Use chia seeds to help thicken a pot pie
If your problem is that a pie with 3 cups of liquid (750 ml) was runny with 2 tbsp of corn starch and some water sucking ingredients such as potatoes, and you say it tasted like corn starch, then you probably just didn't thicken the starch. You should try cooking the original recipe correctly before deciding whether to change it to something exotic. 

Starch needs to be cooked to almost 100 Celsius to thicken. It is certainly above 90 for all types of starch. After thickening, it practically has no taste. Use a thermometer to ensure that it happened, 96 should be a good temperature to aim for. 

You can probably thicken it with chia seeds instead of the starch, although I can't tell you the exact procedure and would like to see somebody posting an answer which explains how to do it. You might or might not like the result, which will be very different from a starch thickened pot pie.