In a dry skillet over medium heat, warm a tortilla for about 45 seconds to 1 minute on each side. The tortilla should begin to puff up slightly. Remove tortilla from pan, and fold in half to create a crease. Spread 1/4 of the bean mixture on half the tortilla and top with a 1/2 cup of spinach, 1/4 cup cheese and 1/4 of the avocado slices. Press the top half of the tortilla down and set aside. Repeat with remaining tortillas.