I make an 8 oz bottle (which turns into just over 9oz once the formula is mixed) and it hasn't leaked yet...but I do use a thickener and maybe that is why it doesn't leak? If you find you are getting leaks you could mix the formula as regular and pour out the one oz that would put it over the line into a bottle that you put in the fridge, then once you have two or more ozs add it to another bottle (so only make a 6 oz or 4 oz bottle that time). That way if you still want to continue to try to make individual bottles you can!