There were far fewer restrictions on obtaining precursors to drug manufacturing as compared to today. It's extremely difficult, but made much easier if you're not doing a total synthesis, for example if you obtain ergotamine tartrate and other precursors.
Anyone interested in LSD manufacture definitely should check out the Hamilton's Pharmacopeia episode with Casey Hardison. Shortened version here: https://youtu.be/Mj2grxdQLQs He was a bit of a genius too, explains some issues around ergotamine tartrate and also how he got busted. Casey is famous for the self-represented "cognitive liberty" defense of his offenses, which of course failed.