Source: Kelly, S. M., et al. Dissection and Immunofluorescent Staining of Mushroom Body and Photoreceptor Neurons in Adult Drosophila melanogaster Brains. J. Vis. Exp. (2017).
This video describes a method of mounting intact brains from adult flies under a bridge slide and shows the protocol performed on immunostained brains for fluorescent microscopy.

