We were in Harvest Caye in November 2022. Great place! We took the tram ride to the Caye from the ship and walked to the ferry area to go to Placencia. You cannot miss the ferry ticket area. They sell tickets for all water trips. They sit you in a large, covered area. Note many others are waiting for numerous other events, so stay alert for the Placencia ferry is that is your choice.
Harvest Caye is beautiful, and I would go back tomorrow. We liked Placencia but would have stayed on Harvest Caye with its beautiful scenery.