Grant Thompson, “The King of Random,” makes a trip to the home improvement store and puts together a pretty decent looking stealth shelf.
He uses a 1″x12″ common board along with some crown molding, finishing nails and some hardwood emboss rope. Some work on a chop saw later and a set of cabinet hinges and coat of sealant gets you a shelf with a hidden compartment. Some rare earth magnet switches help secure the shelf. Diamond plate accents give it some swag appeal.
The gun shown in the vid is a Glock then a Japanese airsoft HK, but your mileage may vary.
Of course as a disclaimer, always remember proper firearms safety and security.