How to make giant fork and knife ?

How big? You can make one from cardboard of foam core board. Then paint or embellish as you wish.

You can cut it out of a piece of wood. Also check thrift stores to see if they have some that have been donated.

You could try plaster make a mold out of foil or wood and cut one if you look around in like good will or vintage stores you could buy the older ones our parents use to put on the wall for like a dollar there 2 feet tall I have seen them check ebay

https://www.pinterest.com/pin/10836855324224526/

https://www.instructables.com/id/How-to-Make-a-giant-fork-with-2-macaroni-noodles/

https://acraftedpassion.com/dining-room-wall-art-giant-utensils/

You can use actual knives and forks to make this. Decide how big you want these utensils to be and then experiment (by just laying them out) how many of each utensil you would need. Say you used two forks for each tine of the "big" fork and maybe four across for the base of the tines, then however many you need for the handle of the fork. You ask for suggestions, not suitability or desirability of the idea. But I would re-think the whole idea. Makes me think of Marie and Franks kitchen in "Everybody loves Raymond"