If you're in a hurry or need chia seeds to thicken a liquid quickly, you can soak them in lukewarm water for as little as 15 to 30 minutes. This will allow them to absorb some liquid and form a gel-like consistency. For a more thorough soaking, leave chia seeds in liquid for 2 to 4 hours. This will give them enough time to expand and fully create a thicker gel.