I went on CIC and I understood that the foreign worker need express entry and then the employer can hire him so only once in the pool
Express Entry is for individuals to gain Permanent Residency Status; once you're a Permanent Resident, you can work legally in Canada. However, someone doesn't need to be a permanent resident in order to be hired (for example, someone can get a temporary work permit).
Additionally, 'being in the pool' only means that someone has submitted a profile to be considered for an invitation to apply for permanent residency; it does not grant work authorization, so you would not be able to 'hire someone once in the pool'.
You appear to be misunderstanding the purpose of Express Entry. As other persons on this forum have indicated, it has nothing to do with employers trying to hire workers.
If you're interested in hiring a foreign individual who neither has permanent residency, or a temporary work permit, or any other kind of work authorization in Canada, and can't find the information you need on CIC's website, it's best if you reach out to an attorney for assistance.