Preheat oven to 400 °F (200 °C). Line a rimmed baking sheet with parchment paper and set aside.
Combine the ground flax and water in a small bowl. Set aside for 10 min. It will thicken and gel up a bit.
Heat oil in a large skillet over medium heat. Add onion and sauté until softened and lightly browned. About 3-5 minutes.
Add garlic and sauté for 1 minute. Now add Italian seasoning, crushed fennel, and red pepper flakes. Sauté for 30-60 seconds until fragrant.
Add mushrooms and sauté until softened and slightly browned. Cook for 5-7 minuted until they reduce in size and release their moisture. You want the pan to be dry. Now add the tamari and cook for 1 minute. Remove from heat.
Add the chickpeas to a large food processor container. Pulse a few times to break down beans.
Now add the cooked mushrooms, oats, breadcrumbs, flax egg, Worcestershire Sauce, tomato paste, salt, and pepper to the processor. Process until well combined and it ALMOST forms a paste (about 30-60 seconds). You don't want it completely smooth so leave some texture. You just want the ingredients to stick together well (see process photos above for example). Taste and add more seasoning if needed. Place mixture uncovered in the freezer for 20-30 minutes (or in the fridge for 1-2 hours).
Remove mixture from freezer and form into balls using your hands. Roll them until smooth. To keep the size uniform, use about 1.5 tablespoons of mixture (use a small cookie scoop or measuring spoon). Place on baking sheet and repeat until mixture is gone. Spray or brush with oil and place in the oven for 30-40 minutes until golden brown and the outside is dry and firm. Flip the meatballs midway through. Remove from oven and let them cool for 10 minutes on the baking sheet. This helps firm them up. You can now serve them with warm spaghetti sauce or cook them in the sauce for 5 minutes to warm them up. Enjoy!