Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Galway to Carcassonne as you normally would.
Carcassonne Salvaza (CCF) is the airport you will fly into if you book a flight from Galway to Carcassonne. You should not have trouble finding flights to Salvaza from Galway; the airport handles an average of 0 inbound flights from Galway per day. You should also have plenty of airline options to choose from since 0 airlines have flights to the Carcassonne airport from Galway. It is only a 2.3 mi journey from Salvaza (CCF) to Carcassonne’s city center.