An emerging new trend reveals that potent synthetic cannabinoid receptor agonists (SCRAs) that were prevalent prior to the Chinese class-wide ban in July 2021 have remained on the market or re-emerged. This is likely because of a new production route where unscheduled tail-less precursors are converted into the desired controlled SCRA via a one-step synthesis. This study reports the discovery of a clandestine production site in Switzerland for this synthesis. Controlled recreations of the synthesis of ADB-BUTINACA (also known as ADB-BINACA or ADMB-BUTINACA) and MDMB-4en-PINACA based on a recipe recovered from the Swiss production site were undertaken. The recreations yielded oils or waxy products with chromatographic purities ranging from 39.3 to 93.4% with the precursors (ADB-INACA or MDMB-INACA) remaining in all products. Mixtures of a precursor (e.g., MDMB-INACA, ADB-INACA, AB-INACA, MDMB-ICA, ADB-IATA, MDMB-5'Me-INACA) with corresponding final SCRA(s) (e.g., MDMB-4en-PINACA, 4F-MDMB-BUTINACA, MDMB-BUTINACA, MDMB-FUBINACA, ADB-BUTINACA, ADB-4en-PINACA, AB-CHMINACA, 4F-MDMB-BUTICA, ADB-FUBIATA) were found in 28 forensic casework samples in the US received between February 2023 and February 2024 and 87 samples seized from the Scottish prisons between February 2023 and July 2024. In vitro CB(1) receptor activity of the precursors, synthesized products, and mixtures of precursors and final SCRAs were examined using β-arrestin 2 recruitment and intracellular calcium release assays. The precursors were much less potent than the final SCRAs and the concentration of the final SCRA dictated the activity of mixtures. This study raises awareness of the emergence of a new production method for SCRAs as observed in multiple countries.