There used to be a hatch that was over the bunk, but it was not installed correctly.  Previous owner did most of this repair but left the actual mast step on.  I took it off and redid directly under the mast.  I dug out all the rotten wood, filled all the hole, then put in balsa core.  On top of that, I made a step pad by layering up fiberglass, approx 30 layers to create the raised platform. On top of this goes the mast support.