Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Waco to Houston as you normally would.
For a flight from Waco to Houston, you will be flying from Waco. Waco (ACT) is just 6.2 mi from the center of the city. Waco is the only Waco airport and it handles 0 outbound flights to Houston per day. 1 airline has flights to Houston from Waco on a regular basis.