Autolyse. Combine all the flours and the water, mix, and let stand covered at least 30 minutes.
Mix the starter into the flour and water mixture, and let sit another 30 minutes. (you probably wan't to feed / replenish your starter after taking the 240 grams)
Sprinkle the salt on top and fold and pincer it in. Let set, covered, for 1 hour.
Perform 3 stretch and folds of the dough, 1 ever 30 minutes, for 90 minutes. Let sit another 30 minutes when done.
Flour (with rice flour or something low in gluten) a banneton. Place the loaf in the banneton. Leave to rise in the fridge, covered, for 12-20 hours. (I just baked when convenient the next day, which was about 17 hours)