Weigh your empty jar and label the jar with the weight. (This comes in handy later if you want to measure your starter without fully emptying the jar.)
Add 50 grams of brown rice flour and 50 grams of filtered water to the jar.
Stir until well combined.
Set aside in a warm spot for 24 hours.
Day 2:
Add 50 grams of brown rice flour and 50 grams of filtered water to the jar.
Stir well and set aside another 24 hours.
Day 3:
Note: At this point you may be seeing bubbles in the jar. It may also have a distinct smell of acetone or another unpleasant aroma. This is normal. Keep going.
Remove 50 grams of the starter (about half) from the jar and throw it away. (Do not save your discard until your starter is well established, after day 7.)
Add 50 grams of brown rice flour and 50 grams of filtered water to the jar.
Stir well and set aside another 24 hours.
Days 4, 5, 6, and 7:
Note: Over the next few days, the starter should be getting very bubbly and starting to rise up in the jar. You should start to notice a pleasant yeasty aroma.
If your starter is bubbly and almost doubling in size in the jar, start feeding 2 times per day.
Feed every 12 hours with a 1:1:1 ratio:
50 grams starter + 50 grams brown rice flour + 50 grams filtered water.
Day 8 and on:
If you have had at least 3 days of strong bubbles and the starter has a pleasant, yeasty aroma – the starter is ready to use. Keep feeding daily for one more week to strengthen your starter. After that, you can store in the refrigerator if you don't plan to bake or feed as often.