The procedure is pretty straightforward, log into the MOM WorkRight portal using your Singpass after baby is born, then fill in the Government-Paid Maternity Benefit claim form; your NOA is exactly the proof they need to establish your self-employed status, so you're already on the right track. A friend of mine who freelances went through this and said to also make a statutory declaration confirming you're self-employed, which is a standard step for our category. Do check your household income too, because if it falls below a certain threshold you may qualify for additional subsidies on top of the maternity benefit, worth looking into before you submit.