Once a child is happy to play with the other children/on their own/with their key person and happy for the parent to quickly pop out of view, then we attempt a longer separation. The parent must always tell the child they are about to leave (to go to the toilet/get a cup of tea/make a phone call) and tell them they will be back soon. It really helps here if the parent can keep a positive tone to their voice and not cuddle their child too much (we know this can be very hard as leaving your child can be very emotional for parents, particularly if the child appears unhappy).
Once the parent has said they are leaving, they must then (supervised) leave the main play room, even if the child cries, the parent is still encouraged to leave. If the child is very upset we suggest the parent counts to 30 then comes back into the room. The child needs to understand that when their parent says they will come back they do return. This is then repeated a few times, gradually increasing the amount of time the parent spends out of the room. The aim is that the child can be settled by their keyperson and are happy to play.