I parked at the H.H. Buckman Lock Visitors Area (seemingly shut down) and walked the mile down Buckman Lock Road, crossing FL 19. There, you will see the FT (Florida Trail) sign and be tempted to go straight in, circumventing a gate. Look instead to your immediate right, and you will spot a small bridge made of just a few planks. Cross that, and you will not miss the trail to your immediate left leading into the woods.
The trail back here has many beautiful views including several ponds and great hiking views, yet remained a mystery to me on initial visits. The trails are made of old roads shaped like a tiny neighborhood, yet I saw no homes, abandoned or otherwise. Also, the roads aren't entirely abandoned as I saw fresh tire marks, most from tractors but some from trucks, with trash dumped in some areas.
I have since been contacted by the Putnam Land Conservancy (PLC) who explained this area is a failed and abandoned subdivision known as the Mondex Complex. It is comprised largely of wetlands with the ponds I saw intended as retention pools when the Mondex Complex was still being developed. Mondex's wetlands function as the headwaters for Camp Branch Creek, a tributary of the St. John's River, with the runoff feeding 404 acres of floodplain, according the PLC whose intention is to restore this area of mesic and wet flatwoods, floodplain, and hydric hammock that serve as a home to a wide variety of plant and animal species including black bear.
The trail is easy to follow with orange markers and I understand leads to FL 20. I turned back after a few miles in, with a 7.2 mile hike round trip. Very peaceful and nice back there, and the ponds offer great viewing, especially if you like dragonflies!