Make seed culture: Combine 1 ounce of the flour and 2 ounces unsweetened pineapple juice in a large glass or small nonreactive bowl. Cover tightly with plastic wrap and leave at room temperature (about 70°F), stirring vigorously with a wet spoon twice a day. Bubbles should appear after 24 to 36 hours. After 48 hours, add 1 ounce flour and remaining pineapple juice, stirring to incorporate. Re-cover with plastic wrap and leave at room temperature, stirring with a wet spoon twice a day. When it is foamy, in 1 to 4 days, combine 2 ounces flour and 1 ounce filtered or spring water in a medium nonreactive bowl. Add seed culture, stirring to incorporate, and re-cover with plastic wrap. Stir twice a day to aerate.

When mixture has doubled in bulk, in 1 to 2 days, convert it into a starter: Combine 12 ounces flour and 9 ounces filtered or spring water in bowl. Add 4 ounces of seed culture mixture (discard the rest, or use to make a second starter) and mix until fully incorporated. Transfer to a lightly floured surface and knead for 2 minutes. It should have the consistency of bread dough. Transfer to a nonreactive bowl and let rest at room temperature until it doubles in size, about 4 to 8 hours. Knead lightly, then store in container with tight-fitting lid (container must be large enough to let starter triple in bulk). Store in refrigerator.

Every 5 to 10 days the starter will need to be fed with more flour and water. Follow the directions in step 2 above, substituting starter for seed culture.