Add the mussels to a large mixing bowl filled with cold water and flour and let sit for about 15 minutes.
In a large heavy-bottomed pot or large Dutch oven add the bacon to the pan and turn heat to medium. Cook the bacon, stirring occasionally, until crispy and the fat has rendered, about 6 to 8 minutes. Use a slotted spoon to remove the bacon to a paper towel-lined plate and set aside, reserving as much fat in the pot as possible.
Return the pot to heat, add the olive oil and heat through. Add the onion and sauté, stirring occasionally, until soft and opaque, about 5 minutes. Stir in the garlic and cook until fragrant, about an additional 30 seconds. Pour in the wine and bring to a simmer then add the tomatoes, red pepper flakes, salt and pepper.
Drain the mussels and rinse with cold water then add them to the pot. Cover and steam the mussels until they open, about 8 minutes.
Serve in large bowls topped with basil and bacon with grilled bread for dipping.
Notes
*Note: If any mussels have cracked shells or do not open after being steamed, discard them, it may mean they are dead prior to cooking and may be bad.