First, run the frozen spinach under warm water until soft. Then, squeeze out all the water from the rinsed spinach.
Add the rinsed spinach and sundried tomatoes to a blender or food processor and blend together. Remove and set aside.
Next, add the chickpeas to a large mixing bowl and use a potato masher to mash the chickpeas. Then, add in the spinach and sundried tomato mixture, flax egg, lemon juice, salt, garlic powder, and black pepper, and continue mashing until a thick mixture forms. It's okay to leave some chickpeas whole for texture.
Then, add in the oat flour. Use the potato masher or a fork to mix together until all the flour is incorporated. Then, cover the mixing bowl and add the chickpea spinach mixture to the fridge to sit for 15 minutes.