Then King Ahaz went to Damascus to meet Tiglath-Pileser king of Assyria. He saw an altar in Damascus and sent to Uriah the priest a sketch of the altar, with detailed plans for its construction.
References for 2 Kings 16:10
So Uriah the priest built an altar in accordance with all the plans that King Ahaz had sent from Damascus and finished it before King Ahaz returned.
When the king came back from Damascus and saw the altar, he approached it and presented offerings on it.
References for 2 Kings 16:12