I would like to ask about rocking the cots. After putting the child into the cot, what is the best way to make a child sleep? Is it just leaving the child to sleep on his own? Maybe pat the child, but then we have to bend for a long time? Please provide suggestions.

There are many & varied ways to settle babies for sleep & these will vary on the age of the baby/child & parent/carer preferences.

How old is the baby you are referring to?
Are you asking as a Early Child Care Educator or parent?

Red Nose has a comprehensive Information Statement that may provide some guidelines.
https://rednose.org.au/article/settling-information-statement