Originally - India and China. Now "constructors" for synthetic cannabinoids are sold on the darknet, and most often buying spice, most likely you will be dealing with a substance illegally produced in Russia, and most likely of lower quality than before, since the production of spice in India and China was still carried out by specialist chemists in laboratories where it was possible to determine the purity of the substance and conduct research on rats, and now this is done underground "according to instructions" from the reagent seller, and the quality and cleanliness is determined immediately in public, without special equipment.
I don’t know where it is produced and I don’t advise you to know. if you are interested in drugs, try something ordinary, not this rubbish. take a look here.
Shit, not. Do not. Seriously. I'm not against drugs, but you need this stuff. So you want something forbidden, take herbs, but at least amphetamine, you will be more whole. Read about the consequences of spice, even I did not try.
I cannot vouch for the accuracy, however, most designer drugs, in particular spice, are produced in China (it is quite logical, given that copies of world brands are made there).