2 Proposals: TrueOS install medium: Inform about an additional option to complete the last step of TrueOS' installation process. TrueOS Handbook: Change Chapter 1.3.3. to make the installation of TrueOS in VirtualBox easier.

[BlazeTester]

Proposal regarding TrueOS' install medium:

After the complete transfer of installation files from the optical drive to the hard disk, TrueOS' install medium shows a screen with the following text:

"TrueOS is now installed!
Click "Finish" to reboot the system.
After rebooting, you may need to eject the install media to ensure the system boots from the local disk."

I recommend to replace this text either with the text

"TrueOS is now installed!
Click "Finish" to restart the computer.
Then, as soon as the computer's start screen appears, you'll have to perform one of the following actions:
Either
go into the BIOS/EFI menu to change the boot order to hard disk first
or
eject the install medium to ensure the computer boots from the hard disk."

or with the text

"TrueOS is now installed!
Click "Finish" to restart the computer.
Then, as soon as the computer's start screen appears,
go into the BIOS/EFI menu to change the boot order to hard disk first
to ensure the computer boots from the hard disk."

I recommend this replacement because removing an install DVD from an optical drive in time is very difficult:
When I press the eject button on my optical drive as soon as the computer's start screen appears, my optical drive opens; but then, my optical drive retracts its disc tray by itself 3 seconds later so that I have no time to remove the install DVD, and therefore, my computer will boot from the optical drive again.
If I recall correctly, the behavior that an optical drive retracts its open disc tray is a part of the normal device initialization on every computer when the BIOS/EFI checks that drive.
Therefore, when an user opens the optical drive, he'll have only a few seconds to remove the install DVD from the open disc tray, and maybe jams his fingers when the drive closes.
Furthermore, I think that your phrasing "you may need to eject the install media" is too unobtrusive. Compared with this, my suggestion "you'll have to perform one of the following actions" emphasizes the necessity that the user has to take action in order to prevent TrueOS from booting from the install medium again.

Proposal regarding TrueOS Handbook Chapter 1.3.3.:

I recommend to replace the text

"Once the selections are made, click Create to finish using the wizard. The virtual machine will now show up in the left box, as seen in the example in Figure 1.3.8."

with

"Once the selections are made, click Create to finish using the wizard. The virtual machine will now show up in the left box of the VirtualBox Manager.

The following text should be written in a blue Note Box:
To optimize the installation process of TrueOS, it is recommended to adjust the Boot Order in the System tab of the virtual machine:
The entry "Hard Disk" should be moved to the first position in the Boot Order list.

That way, the installation process of TrueOS is still able to start because VirtualBox will skip the empty Hard Disk and will boot from TrueOS' install medium in the Optical Drive.
After the transfer of TrueOS' installation files from the Optical Drive to the Hard Disk, the virtual machine has to boot from the Hard Disk to complete the installation process.
With "Hard Disk" on the first position in the Boot Order list, TrueOS will conveniently boot from the Hard Disk during the last step of TrueOS' installation process.

(By performing this adjustment, you prevent the following situation:
VirtualBox' default boot order (Optical Drive first, Hard Disk later) would lead to the problem that after the transfer of TrueOS' installation files from the Optical Drive to the Hard Disk, VirtualBox would unnecessarily boot from the Optical Drive again. In this situation you would have to close the window of the virtual machine, choose "Power off the machine", and remove TrueOS' install medium from the Optical Drive in order to complete the installation process of TrueOS)."

Additionally, I recommend to replace Fig. 1.3.8 with a screenshot that shows the optimized Boot Order "Hard Disk, Floppy, Optical".
(Maybe you'd like to erase the entry "Floppy" completely - especially if TrueOS doesn't support Floppy drives anymore).
As I use an older version of VirtualBox, I don't send you a screenshot because my screenshot wouldn't harmonize with the other VirtualBox screenshots in your handbook.

Then, the text below Fig. 1.3.8 should be changed from
"Fig. 1.3.8 New Virtual Machine “test”"
to
"Fig. 1.3.8 New Virtual Machine “test” with optimized Boot Order"

I recommend this alteration because the actions described in my proposed text above

"Either
go into the BIOS/EFI menu to change the boot order to hard disk first
or
eject the install medium to ensure the computer boots from the hard disk."

are hardly doable in VirtualBox:
A virtual machine restarts so quickly that an user easily misses the second in that he is able to press F12 to temporarily change the boot order of the virtual machine. To eject an ISO image from the Optical Drive, he has not enough time at all.
On top of that, my alteration could prevent a situation like https://discourse.trueos.org/t/how-to-start-trueos-in-virtualbox/760