||While it is possible to make GHB using materials aquired from hardware or other stores, it won't be the only thing you make or leave in there.|
The important thing in any successful chemical reaction is not the making of the product, but the purity and workup to isolate your product or at least leave it in an acceptable state. This is particularly true for pharmaceuticals or other chemicals intended for internal use. There are very strict guidelines to chemical purity and manufacturing proceedures for drugs for a reason.
Materials purchased at a hardware store or other "over the counter" locations are not intended for use in drug manufacture, and you risk serious damage to yourself or others by using such materials. While GHB is extremely easy to make, chemically speaking, the fact that it is made with the intention to injest requires you use the purest starting materials possible. This reduces the risk of leaving heavy metals (such as lead), other organic materials (oils, possible carcinogenic or toxic products) in your final product or the accidental manufacture of "side products" (products made by the reaction of impurities in your starting materials, which can sometimes be more toxic than the impurities themself).