After consolidating his rule, Solomon’s called Israel’s leaders together at Gibeon, the most important of the high places (1 Kings 3:4) because of the Tabernacle:
2 Chronicles 1:2-3 Solomon called together all the leaders of Israel—the generals and captains of the army, the judges, and all the political and clan leaders. Then he led the entire assembly to the place of worship in Gibeon, for God’s Tabernacle was located there. (This was the Tabernacle that Moses, the Lord’s servant, had made in the wilderness.)
The event included sacrificing 1000 burnt offerings:
2 Chronicles 1:5-6 So Solomon and the people gathered in front of it to consult the Lord. There in front of the Tabernacle, Solomon went up to the bronze altar in the Lord’s presence and sacrificed 1000 burnt offerings on it.
One thousand burnt offerings is, well, a lot. They were most likely male cattle, sheep or goats from Solomon’s own flocks, with no defects, according to the Law (Leviticus 1):
Leviticus 1:2 When you present an animal as an offering to the Lord, you may take it from your herd of cattle or your flock of sheep and goats. If the animal you present as a burnt offering is from the herd, it must be a male with no defects. Bring it to the entrance of the Tabernacle so you may be accepted by the Lord.
The procedure was complex: the animal had to be slaughtered, its blood drained, and then it was cut into pieces and burned on a purpose-built fire.
This all takes time. It would have taken weeks, if not months.
But it was an important investment for Solomon wanting to establish his validity as the king of Israel, both through his wealth and his dedication to the Lord.
That Bible blog 