For the beans: Place the beans in a large bowl and cover with cold water. Soak overnight. Drain and rinse the beans and place them in a large pot with the garlic, bay leaf and thyme. Bring to a boil and then turn down to simmer for 1 hour, until very soft. Drain the beans.
Preheat oven to 425 degrees.
First make the crostini. Spread the bread on a baking sheet, drizzle with oil and sprinkle with salt and pepper. Place in the oven for 15 minutes.
Heat a medium pot over medium heat and add 3 tablespoons of oil. Add garlic, salt, red pepper flakes and rosemary and cook until fragrant, 1 to 2 minutes.
Stir in beans, zest and lemon juice and continue to cook. Mash beans with a potato masher or the back of a fork. (For a smoother dip you can puree the beans with an immersion blender.) Garnish with parsley. Spread some of the beans on the crostini and leave some to dip with carrots and celery.