You should have a baffle on the speaker which is the ceiling itself. Unless you have substantial air leaks between the ceiling and the room below you shouldn't require any other "box". Why do you think you need a box?
I thought I would need something to act as a cabinet. And I will need to put about 8" of insulation over top of this,so I thought putting it directly over the speaker (potentially even touching the cone) would be a bad idea?
A cabinet is a convenient way to hold speakers. An enclosure is composed of a top and bottom, two sides and two baffles - front and rear. You have a front baffle - the celing - which will keep the backwave from wrapping around the driver to interfere with the front wave. That's the purpose of a baffle in a sealed (acoustic suspension) enclosure.
Unless the baffle has air leaks or is very small, a baffle with the speakers mounted on it is all you need. No box. No insulation.
This would be termed an "infinitie baffle" if the driver's longest wavelength is shorter than the longest dimension of the baffle.
Listen to the speaker without insulation behind it. Insulation serves different purposes in a speaker enclosure. One purpose is to make the enclosure appear larger than it really is by attentuating the backwave of the driver. This is unnecessary in an infinite baffle. A layer of insualtion on top of a ceiling mounted speaker can provide some help if the backwave of the driver is firing into another hard surface such as the floor of the room above it. Otherwise, if the speaker is working into an attic space, a thin layer of insulation would simply keep the driver from collecting dirt and dust.