The left front side drive holder can be removed from the case by unscrewing 3 screws and sliding the drive holder back. You will need to remove the left drive holder from the case in order to access the screws for drives in the right drive holder.

Install the drives for the left drive holder while it is out and then attach the drive holder back in. Make sure to connect the drive cables while the drive cage is out as it will be harder to reach the 3.5" drives under the 5.25" bays when the system is all together.

It is possible to work around the drives when they are installed, but it more difficult. You will also notice that the spacing above the bottom drive is not as good as the other drives.