Well, of couse you "can" flush right away after your first flush.
However this is not recommended.
First of all a flush is a strain for the body and secondly the stones in the liver need some time to move forward via outlet.
So, unless you don't have the urgend need because you feel there is something in your liver that wants to come out asap it would be wise to let 2 to 3 weeks elapse before flushing again.
Blessings