You can find some helper scripts here:
https://github.com/Preflex/easy-chroot

ManChroot.sh will give you a root shell inside the chroot.
DeskChroot.sh will launch a XFCE4 session.

You may notice errors about mount points in /home/nemo not being found. If you would like to share these directories with the chroot, create those directories inside the chroot.

You can find the preconfigured Manjaro rootfs here: https://github.com/Preflex/easy-chroot/releases

To use with the helper scripts, unpack it in /opt/easychroot/Manjaro

This rootfs contains helper scripts in /usr/share/easychroot/scripts/
The start_xwayland.sh contains hardcoded values for my Nexus 4's screen. If you are using a different device, you will need to edit the last line of this script, substituting the height and width values for your device.