I recommend feeding your sourdough starter in the morning around 8-9am.
In a large mixing bowl, combine the active sourdough starter, salt, and water. Mix well.
Add the flour and mix until completely incorporated (all flour absorbed). Cover and rest in a warm environment for 30 minutes.
Perform one fold, as explained: Imagine the bowl divided into 4 corners. Gently scoop from the bottom and lift up one corner without the dough breaking as high as it’ll go, then fold toward the center of the dough. Rotate the bowl to the next “corner” and repeat. Repeat for a total of 4-6 times.
Cover and rest the dough in a warm environment for 4-12 hours, until doubled in volume. Perform 3 more folds periodically through the day. (For example, I'll put the sourdough in the fridge around 9-10pm.)
Put away in the fridge overnight, 8-12 hours.