"This salad came about when some friends gathered for a potluck-- each of us was supposed to bring a certain color food, and I picked green. Could also omit the spinach and serve with tortilla chips or crackers."
Halve avocados and remove the pits and peels. Cut each half into 6-8 slices, then roughly dice. Put into a medium bowl with lemon juice; toss to coat.
Mix in green bell pepper, green onions, and black beans. Stir in salsa, garlic, and salt and pepper.
Put 2 cups of spinach in a medium serving bowl. Layer with half of the avocado mixture. Then make another layer with the remaining 2 cups of spinach, and top it off with the other half of the avocado mixture. Let sit in the fridge for 1 hour for flavors to meld.