Combine the ground beef, canned tomatoes, and taco seasoning in a slow cooker. Cook on low for 6 – 8 hours.
Either serve the taco salad right away with warm meat, or chill it overnight before assembling salads for transportation to picnics.
To assemble the salads, layer ingredients in the following order: salsa, onion, avocado, beans, taco meat, tomatoes, lettuce, cheese, and tortilla chips. (You might want to take the tortilla chips with you and add them just before serving.)
Feel free to adjust the amounts of each layer to your liking.