Update: You can purchase your day pass for entry into Fort Boggy State Park ahead of time. Go to
https://texasstateparks.reserveamerica.com/, enter Fort Boggy State Park, select day passes, arrival date (April 17, 2021), select not flexible, and 1 day for length of stay. For more detailed instructions, please see this video:
https://www.youtube.com/watch?v=JZfP0USJq0Q
You can still pay the day of the event at the park. Cash is strongly encouraged. Last time, I believe the credit card machines were down. Admission is $3 for adults, and free for children aged 12 and younger.