I have been making chunks by duplicating a 'template' chunk that contains all of the photos in my project and then deleting the photos I don't want to use for the current chunk. But it would be more intuitive for me to be looking at the locations of photos in my template chunk, select the ones I want to use, and have an option to 'create chunk from selected photos'.
An alternative would be to have the Edit > Invert Selection enabled for photo locations. I could make my selection for a chunk, invert, and then delete.