I'd already added deck lines to the boat by the time I went to work on the hatches & bulkheads, BTW.

My first decision was to paint the deck after I was finished the glass work - this let me be more 'quick and dirty' with some steps since the evidence was to be well hidden.

I wanted to make a glass 'hatch recess' and epoxy it to the underside of the deck. The deck underside was smooth (no ribs or reinforcements) in the hatch areas, so I could assume that a mold taken from the topside of the deck would reflect what was underneath.

I used transparent adhesive shelf liner material (Con-Tact brand) as a barrier between the deck and the epoxy/glass mold I built in place. Strips of bending plywood formed the 'ribs' on the mold.

Underside of mold:

I did take some pictures of the 'work in progress' but they were lost in a computer/camera SNAFU situation. Sorry!