Preheat the oven to 350°F.

Spray 5 mini loaf pans or a 12-muffin tin with oil; set aside. (You will have about 4 cups of batter to fill tins half- to three-quarters full, using as many as you need, based on their size. Loaf pans will yield rectangular crackers; muffin tins will yield round crackers.)

In a large bowl, stir together flour, baking soda and salt, and then add raisins, walnuts, sunflower seeds, sugar and rosemary, and toss to coat.

Add buttermilk and stir until combined.

Transfer to the prepared pans and bake until golden brown and firm, 25 to 30 minutes.

arefully turn out onto wire racks and let cool completely.

Preheat the oven to 300°F.

Using a serrated knife, slice bread as thinly as possible (1/4-inch to 1/6-inch is ideal; chill loaves until cold, if you have trouble getting the slices thin enough).

Arrange slices in a single layer on a baking sheet and bake, flipping halfway through, until dried out, about 30 minutes.

Loosen crackers from the tray as needed with a spatula or knife, and then set aside to let cool completely.