Ok so before you read any further this post has no actual basis behind it and this is just a way that they could bring laurel back that i thought of. Im doing this because if the writers cant think of a good way to write her back in, then maybe if they read this they might get some ides.
The writers can think of it themselves of how they made the death look real that shouldnt be too hard
Laurels final words to Oliver was he told her to fake her death because she knows of a larger crime syndicate (Main Villain) inside Star City who are planning on holding her hostage to blackmail lance as captain of the SCPD to allow for their drug trade.
They then had to fake her death to take away that leverage and not tell anyone.
All of this is just bs but its an idea that the producers are more than welcome to use lol.