I'm looking to install a bath fan (https://www.homedepot.com/p/Delta-Breez-GreenBuilder-Series-100-CFM-Wall-or-Ceiling-Bathroom-Exhaust-Fan-ENERGY-STAR-GBR100/204347760) in a bathroom on the second story.
The bathroom doesn't have the attic over it though, and there is about 1' to the roof.
My question pertains as to how to mount the fan though. The manual (https://images.homedepot-static.com/catalog/pdfImages/af/af6d5071-25ee-4203-8969-8983c5237ae3.pdf) assumes that this is "new work" or that the attic is accessible.
Brackets were included in my box, but I don't think I'll be able to use them since the rectangle I'll be cutting is the length of the fan (about 8").
I noticed that there are holes in the side of the box (Marked in the picture) in the picture below. If the fan was placed against one of the joists and then screwed into place from below using the screws provided through these holes, would this be an acceptable technique?