In a small bowl, add ground flaxseed and water. If need multiple eggs, just multiply the ingredients.
Stir with a fork and let sit for 10 minutes, until the mixture is thick, "gloppy" or congealed.
Notes
Store: Refrigerate in an airtight container for up to 5 days.
Can I use whole flax seeds? No, for seeds to thicken they have to be ground.
How to grind flaxseed: Add desired amount of whole flax seeds to a high speed blender or food processor and grind until powder forms. Do not overprocess into paste.
2.5 tbsp vs. 3 tbsp of water: Using 2.5 tbsp of water makes stickier and thicker flax egg.
Let baked goods cool sufficiently: At first baked goods will appear soft. Cool for 45 minutes or longer to allow baked goods to settle into a firmer texture.