Albert Barnes Commentary Leviticus 4:15

"And the elders of the congregation shall lay their hands upon the head of the bullock before Jehovah; and the bullock shall be killed before Jehovah." — Leviticus 4:15 (ASV)

In this case, the imposition of hands is performed by the elders on behalf of the nation. But in other respects, the rites were performed by the high priest in the same manner as in the sin-offering for himself.