In my final setup, I placed it upside down on the waste board, in a cut-out, as you can see in my posting. With your tapered holes, you need to place it upright, but this might be not possible, because it might be too unstable. Maybe create a wood block of the same size as the interior of your case. This can be done with the cutter as well, or just a saw and lots of sanding paper for a perfect fit. Then screw this block on the waste board and use my clamp design to secure the case.
The exact positioning of the wood block can be difficult. If the case is not too high, you could screw it first on the wasteboard, then cut it to size with the cutter. Or cut it a bit, then saw the rest. Always use the bottom left quick position in Carbide Motion for the (0,0) position. Then use absolute positions in your design files. This makes it very easy to place the holes at the exact required positions, relative to the fixture block.
Instead of a custom clamp and screwing a fixture to the wasteboard, nowadays I would build a fixture with the vise, this would make it easier to position it perfectly and no extra clamp needed. See at 0:38:
For the holes and cut-outs you can import SVG files in Carbide Create. I think the tapered holes could be created by using different start depths and max depths for the toolpaths with multiple circles.