'Liver cleanses' and 'gallbladder flushes' are not advisable. Firstly, it's impossible to 'cleanse' or 'flush' the liver or the gallbladder with anything. Nothing that you swallow enters your gallbladder at any point in the digestive process, and by the time any nutrients from your drink reach your liver, they will not be in a form that have any cleansing effect. The process does not get rid of gallstones, and drinking oil is very, VERY stupid for someone who has gallstones as fatty foods aggravate the problem and can cause a lot of pain and inflammation.
Also, no, gallstones are not present in the liver. They can pass from the gallbladder into the stomach (which tends to be very painful - trust me, I've experienced it) but not into the liver. There are no stones in your liver. If you want a healthy liver, drinking epsom salts, olive oil and apple juice is not going to help you in the slightest, and will simply make you feel ill and cause you to pass lumps of undigested solidified oil in your excrement (which people often mistake for 'stones' - hence the myth that this 'detox' flushes out gallstones).
If you want a healthy liver, then eat healthily, don't consume too much saturated fat and only drink alcohol in moderation. It really is that simple. 'Liver cleansing' is a quack remedy that achieves nothing, and will likely make you feel nauseous and do you more harm than good.
Think about it: if it was possible to cleanse the liver in this way, doctors would recommend it and health insurance companies would make do this cheap process rather than paying out for them to have bona fide medical treatment.