You may also read this: https://onlinelibrary.wiley.com/doi/full/10.1111/j.1541-4337.2008.00064.x
(I guess there are many places where cassava is considered as the staple food, and they just cut them into small pieces, crushing, pounding, cooking and filtering out the water a few times are all simple methods applied to reduce the HCN content. Sundrying might be another way since sundried cassava is also produced and exported by many countries.. Finally its the method and period of time of its application is what makes the difference.