Leviticus 1:11

1:11 and must slaughter it on the north side of the altar before the Lord, and the sons of Aaron, the priests, will splash its blood against the altar’s sides.

Leviticus 1:15

1:15 The priest must present it at the altar, pinch off its head and offer the head up in smoke on the altar, and its blood must be drained out against the side of the altar.