Trim new side decking. Rebate for, make, and glue in hardwood deck edging and radius. Spot fill decking and fibreglass. Fill and fair.
Mark out, drill and counterbore for companionway hatch bolting. Make copper bolts and dry assemble hatch.
Position and fit hatch slide rails. Drill, counterbore and screw down rails.
Trim hatch sides to fit. Make and rebate in brass runners. Slot rails to accept hatch and assemble.