The bad news is that ricin is relatively easy to make and can be extracted from castor beans which are widely available. The LD50 is also very low. (LD is Median Lethal Dosage). The term refers to the amount necessary to kill 50% of the test subjects, typically mice. In the case of ricin, the dose is 22 micrograms per 1 kilogram (2.2 pounds) of adult weight. So, it takes very little to be fatal.
I was going to go into the chemistry of ricin production but have reconsidered and want to provide only information about ricin and not a guide to isolate it. There are many good articles concerning this poison and I will leave it to our readers to pursue any additional information.
One final thought is that castor oil that is made from that same castor bean does not contain ricin. The ricin is destroyed by the denaturing process in the manufacture of the oil. And, ricin has been investigated in research for positive chemical possibilities. So, there is very little to fear about this material when we are prepared to use caution and exercise good judgment.