Note if you want to make your filling on the stove with the same method this will save you 3 hours and having to clean your slow cooker to use again (unless your like me and have more than one)...
Once you have diced all your ingredients put your mince and onion in the slow cooker on high to brown. Now add your taco seasoning and mix thouroghly. Add garlic, tomato, carrot, asparagus, spinach, tin tomato and salsa and cook until all soft. This was 3 hours on high for me.
Put filling aside and clean your slow cooker ready to use again or if your lucky and have more than one start the next steps.
Layer tortilla (I used 1.5 tortillas for each layer in my 6.5L), a layer of filling, thin layer of sour cream, layer of cheese and repeat until all used then top with lots of cheese. I cooked mine on high with a tea towel under the lid for 5 hours