I’d be recommending option 2. Once the shim is in the pocket and completely dry, you can do a test fit for the neck and adjust if needed.
option 1 will be a gluey, slippery nightmare.
option 3 as option 1 with the added complication of trying to glue and clamp small bits of shim that will want to move everywhere but where you need them. At least in the bottom of the pocket, they will be more or less retained while you clamp them.