How to build this..... Brett

Build it out of plywood and then cover in glass. Would be an easy project, look up my topic on how to make epoxy fillets.

 

There's a multitude of solutions for this project.
Build from Starboard and angle aluminum or build from wood,
then mechanically fasten to runners fiberglassed to the deck.
Build from wood, cover in fiberglass, then glass to the deck.
Build from fiberglass panels, then glass to the deck.
Build a disposable mold, layup in fiberglass, glass to deck.
Glassing to the deck is the easy part.
By the time you get done building the grab
you'll have enough experience to bond it to the deck.
Avoid drilling through your deck, less chance of leaks forming.