Heat 1/2 tbsp olive oil in a large skillet over medium/high heat. In a food processor, combine chickpeas, garlic, salt and pepper, and sweet potato. Pules until combined. Add flax egg and pulse until combined, but not entirely smooth. Divide mixture into four balls and flatten to form patties. Cook about 5 minutes on each side until golden and crisp. Repeat with black beans (minus the flax egg)
heat the 1 tsp of olive oil a large skillet over medium heat. Add yellow squash and saute lightly, only a few minutes on each side. Remove from heat once the slices begin to look translucent. set aside on a paper towel.
In a small bowl, mash up avocado. Add lemon juice and mash until combined
Toast bread. Spread 1/4 of the avocado on each slice. On the bottom slices, layer 1/2 spinach, 1/2 red pepper, two chickpea patties, 1/2 squash, two black bean patties, and tomato. Top with the other slice of bread, slice each sandwich in half, and serve.