You could either be out riding and have to fold up a tube and you are in no hurry or at home and want to store some loose tubes well this is how I fold up or should I say roll up my tubes.
Find the stem and make sure it’s facing inwards.
Find the direct opposite end of the tube and start rolling up with the valve released.
You should have a tube that is rolled up neatly. Then just grab a rubber band and whack it around and you’re done.