What do you consider 'minimal'? There's the disc1 CD image. Is that what you're looking for?does FreeBSD have a minimal iso installer?
Mini-memstick doesn't contain installation files.
The OP specifically asked for an installer.No but it is minimal
The OP specifically asked for an installer.
mini-memstick
This can be written to a USB memory stick (flash drive) and used to boot a machine, but does not contain the installation distribution sets on the medium itself, similar to the bootonly image. It also supports booting into a "livefs" based rescue mode. There are no pre-built packages.