Is there currently recurring spawning on the island? I have built on islands many times, my custom when starting my build was to surround the island in a simple wooden walkway using the large floor pieces. I placed workbenches under the walkway so they were out of sight and out of mind. I was never disturbed by anything spawning, but then again there was not much in the way of recurring spawning to begin with, on most of my island builds. I did have some problems with invasions, until I made sure to never have 3 different workbenches on site at the same time.

One problem with building on islands is, "Does its highest point get inundated by waves during storms?" It is nice to be above the highest waves while building, getting lifted off ones feet and floating while building gets old fast ...