Optimal time for the flush is 10 pm (gallbladder and liver energies peek at that time)...
and the flush should be preceeded by 'making the bile ducts open' - which is normally achieved by taking Epsom Salts (some people claim Colosan works too) at 6 pm and 8 pm. I was once miseducated - skipp epsoms, drunk just olive potion and failed badly (sleepless night, no stones passed even though I was full of them)! You don't want to spend a miserable night
You do not eat anything because you want your bile not to be used and therefore the pressure in gallbladder/liver to be higher. If you can, eat only light foods that day or fast.
Eating should be stopped ideally 5-6 hours before drinking first epsoms. Hope that helps (you'd have to shift your schedule if you want to fit 7pm though)