Epsom Salts are in no way similar in effect as oil. The only purpose of Epsom Salts in the Liver Flush is to help dilate the biliary tree and common bile duct so that stones move out with more ease.
Some people use Epsom Salts during a gallbladder attack because the gallbladder is already contracting and it works because it provides extra dilation to let stones pass.
That said, there is no harm in just taking epsom salt, just don't be surprised when tadaaa, nothing happens.