Unbleached white flour and filtered water. It has taken and every 12 hours after it bubbles up and falls I remove half and add back. I’m going to slowly convert it to whole wheat and oats when it’s really tangy. I just started the starter three days ago, so I have awhile before that stage. In a couple of days I will start making crackers with the starter I remove. I’m a great cook, but I must use recipes for baking. That’s science, which was my worst subject!
I'll have an alternative starter recipe for you, but it won't really work until early summer.
Another alternative for you might be a pre-ferment or hold-back method. It's what I use here since this area has black mold which kills any long-term starter. When I make a recipe of dough (I'll give you mine if you like), I hold back 180 grams of dough and save it in a cool spot and add it to the next batch.
johnny