I didn’t realize that the earth really was flat, but this capture of the Golden Gate assures me that the edge of the earth is but a few miles out in the Pacific Ocean. You can see the last bit of the sun sinking behind the edge of this flat earth! One of the pleasure craft shown on the San Francisco Bay, or even the tanker steaming in through the Golden Gate, could easily sail out and touch the sun as it passes below the horizon of this flat earth.
An interesting comparison: this photo showing the sun setting to the south of the Golden Gate Bridge. Three weeks (Jan 7 to Jan 22) separate the two photos, showing how much north-to-south movement in the position of the setting sun there is near the winter solstice.