Another way to do it, which you don’t see often, is to use the installer’s bootloader to boot the installed system. For example, if you are booting in UEFI mode then the installer will first boot into grub2. Here you can drop into the grub2 command-line interface prompt where you could enter something like:
ls
set root=(hd0,msdos2)
ls /
linux /boot/vmlinuz root=/dev/sda2 quiet splash ro
initrd /boot/initrd.img
boot
Once you have your installed system running:
sudo grub-install
sudo update-grub