Place tripe into a saucepan and cover with water. Bring to a boil, then turn off the heat and let sit until tripe has cooled slightly, about 20 minutes. Drain and rinse; cut into 1/4-inch pieces.

Cook bacon in a Dutch oven over medium heat until browned, about 3 to 5 minutes. Add leeks, bell peppers, parsley, onion, and celery; sauté until tender, about 5 minutes. Stir in stock, pepper, marjoram, cloves, thyme, pepper flakes, and bay leaf. Add tripe and bring to a boil. Reduce heat, cover, and simmer until tripe is very tender, about 2 hours. Add potato and carrots; cook until tender, about 20 minutes.

When the soup is almost ready, melt butter in a small skillet over medium-low heat. Whisk in flour and stir until mixture becomes paste-like and light golden brown, about 5 minutes. Stir roux into soup and cook, stirring constantly, until soup thickens a bit. Taste and adjust seasonings as desired. Discard bay leaf.