“house of Baal.” That is, the temple of Baal, just as the “house of Yahweh” is the temple of Yahweh. This temple, as well as Ahab’s palace, sat on Samaria’s acropolis. Herod later built a temple to Augustus more or less over it. When the palace/temple area was excavated in the early 1900s, there was a building discovered that could well be the temple of Baal, but the practice was to fill in each area or strip excavated with the next strip, so the remnants of the Israelite palace/temple are now covered up again.
“the worshipers of Baal.” The Hebrew is technically “those serving Baal,” but the word has the meaning of to worship by serving.
“not a man left.” The culture would be that this worship would be men only, not a mixture of men and women.