Well, in that single post it’s written. I’ve never done it, so lemme try myself:
root@turris:/# mkdir /tmp/mnt-test
root@turris:/# mount -o subvolid=0 /dev/mmcblk0p1 /tmp/mnt-test/
root@turris:/# ls /tmp/mnt-test/
13.info 15.info 17.info 2.info 21.info 24.info 26.info 4.info @13 @15 @17 @2 @21 @24 @26 @4 boot.scr
root@turris:/# ls /tmp/mnt-test/@24
bin boot boot.scr dev etc lib mnt overlay proc rom root sbin srv sys tmp usr var www