You can make use of the Labour Department Interactive Employment Service (http://www.jobs.gov.hk) ......just fill in a form and fax to the Labour Department. They will put the advertisement in the website and their offices.
I employed my home helper through this channel and they have referred three applicants for me to interview. My home helper now works from 8:00a.m. to 6:00p.m. to help me to look after my baby.