As I configured /usr/share/calamares/modules/unpackfs.conf:
---
unpack:
- source: "/run/initramfs/live/LiveOS/squashfs.img"
sourcefs: "squashfs"
destination: "/"
After installation I get in / directory:
# ls -l
total 20
drwxr-xr-x 18 root root 3980 Vas 6 12:34 dev
drwxr-xr-x 2 root root 4096 Vas 6 07:26 LiveOS
drwx------ 2 root root 16384 Vas 6 12:34 lost+found
dr-xr-xr-x 174 root root 0 Vas 6 11:45 proc
drwxrwxrwt 3 root root 60 Vas 6 12:34 run
dr-xr-xr-x 13 root root 0 Vas 6 11:45 sys
# ls -l LiveOS
total 8557572
-rw------- 1 root root 8762949632 Vas 6 07:26 rootfs.img