In a large container, combine seeds and 4 ounces water. Cover and soak overnight.
The next day, combine all-purpose and whole wheat flours in a bowl. In a separate bowl, mix the remaining water and sourdough starter to dissolve. Add the wet mixture to the dry and mix until incorporated. Rest 20 minutes. Add the salt and continue to mix gently by hand for 5 minutes. Rest for 5 minutes. Add soaked seeds and mix until incorporated.
Roll the dough into a ball, place in a bowl, and cover. Every hour tuck the edges of dough under, tightening the dough ball. When the dough has rested for 4 hours, turn it out onto a work surface and divide it into 2 rounds. Rest the rounds 15 minutes and then shape into a batard. The bread can be rolled in more seeds for texture.
Place the bread seem up in a bread basket. Heat oven to 425°F. Let bread rise 3 hours at room temperature, or let rise 1½ hours and then refrigerate overnight. It can be baked right out of the refrigerator. Bake bread 45 minutes, remove from oven, and cool completely before slicing.