To gain access to the interior, you can pull off both side panels. A magnetic dust filter has also been placed on the vent of the metal one to further ensure dirt can't enter the system. The small Y-shaped vent doesn't seem to be sturdy, as you can clearly feel slight dents in the surface. This is also due to the fact that Corsair has opted to use pretty thin metal. To visualize it, we simply placed the panel on the flat table so you can see the issue clearly.
Corsair leans into the modularity of the case quite heavily and the Frame 4000D does certainly allow further disassembly than most modern cases, l leaving just the frame - thus the name seems quite well-chosen. That said, it will be interesting to see if Corsair ends up supporting this further by providing additional parts like alternative I/O ports or color parts and exterior panels. In their blog post announcing the chassis, Corsair does point out that they are planning to have an ecosystem of compatible parts, and they also offer 3D printing files so you could start customizing your case.
The interior layout of the Frame 4000D is pretty traditional overall. Out-of-the-box, the chassis ships with the solid cable channel cover pre-installed, which also includes the GPU support beam.
The shroud is two-part, with the side cover and top panel. There is room for two 120 mm fans if you are going for a traditional GPU setup. Corsair has included two mounting possibilities for vertical GPUs to attach the spacers for a PCIe slot to as well. A large opening towards the front of the chassis is also an interesting choice. While this does give you the possibility to go with any type of thick liquid cooling setups, it would have been nice if Corsair has included some sort of (modular?) cover. On top of that, there are two cable routing holes, which are missing grommets, which also feels like a small oversight overall. The GPU beam may look simple but is actually extremely sturdy. This well-designed bar has a long metal screw within to hold it in place, so big and heavy GPUs will not be an issue either.
Underneath the shroud, you will find a storage mounting plate which can accommodate either two 2.5" drives or a single 3.5" unit. There are three possible placement possibilities so you can adjust things for a long PSU or thick front liquid cooling setup. Above that, the entire front panel will let both light and air in easily and is intended purely for cooling purposes. You may install a radiator of up to 360 mm size here.
In the rear, the PSU bay allows for a unit of up to 220 mm in size to be installed as the shroud actually includes a cover towards the front of the chassis. It will sit on two simple but effective foam spacers and the power supply can easily slide in through this side of the chassis, but you do have to clear the IO wires. Above the shroud, you will find the seven expansion slots and the fan mounting position. Thanks to the elongated mounting holes, you will have some flexibility to adjust the height of any exhaust unit in the rear.
The Corsair Frame 4000 D includes several strategically placed Velcro strips for cable management and the wiring from the IO is actually partially sleeved as well. On the backside of the motherboard tray, you will also find one more HDD tray, bringing the maximum possible storage capabilities of the chassis to a total of four 2.5" or two 3.5" variants. Each of the two trays also has an embossed section where you can easily place your Corsair iCUE Link hub.
Taking a quick look at the ceiling, it is also obvious that this is where you will likely install your AIO with plenty of space between the mounting rail and motherboard area, so that even wide 280 mm units should easily fit without issue.
All wires within the Corsair Frame 4000D are sleeved black and of the default variety. Thanks to the unified motherboard header, that step of the assembly process is as easy as can be.