How do I flag a View Page

You cannot flag a view, because it is not something that Flag supports flagging, such as nodes, comments, etc.
Sorry, thought I was in Flag module. I'm actually trying to do the exact same thing you are right now.

Was this ever solved. Would like this functionality in D8 as well.

Follow up for this. One solution:

1. Create node
2. Using the Insert View module, add your view to the Body field using [view:name_of_view=block_1]
3. Duplicate your current view page display as a block display.

Your view should be now embedded in a node which can now be flagged.

#3 this works as long as the view does not use contextual filters using url arguments.