Installing FreeBSD on installation USB

I have a FreeBSD image on a USB stick but the only available place to install it is on the da0 - the USB stick. Can I install on the USB stick that I am booting from or can I replace the USB stick with another during the installation process... or maybe I can partition a USB to create space for the installation.

Any advice appreciated.
You could try a USB hub so you can plug in more than one USB stick. I'm not sure if it will boot through that though, never tried it.
Alternatively find any machine with 2 USB ports, boot from the one you have, install onto a 2nd USB stick, then move that to your target machine.
I did end up installing FreeBSD on a different machine, although getting it to boot initially took some tome since I need to change the boot option to UEFI, but having done that the installation went OK, and was able to boot my target machine.