Feed your sourdough starter.
Place in a warm spot for 4-12 hours or until active and bubbly.
Take your active sourdough starter and spoon into a silicone muffin cups, ice cube tray, or even just a muffin pan lined with regular muffin liners or plastic wrap.
Freeze until completely frozen for about 3-4 hours.
Remove the frozen sourdough starter from the mold and place in a freezer safe ziploc bag.
How To Thaw And Reactivate A Frozen Sourdough Starter
Place the frozen starter in a jar and let sit at room temperature on a counter covered with a tea towel or paper towel with a rubber band.
Allow to thaw for around 12 hours.
Feed equal parts flour and water. So if you froze 75 g starter: Feed it 75 g of water and 75g of flour.
Leave it at room temperature for 12 hours.
Discard half of the starter and feed equal portions of flour and water. So if the amount of starter you have is about 1/4 cup after discarding, feed 2 tablespoons water and 2 tablespoons all-purpose flour.
Your sourdough starter will be ready to use once it doubles 4-12 hours after feeding.
It may need a few feedings before it is really nice and active.