How to recreate a Debian GNOME live image with customization

[debian.alabaster696@passmail.net]

Hi there,

I want to build a customized live image. For that, the idea is to start 
with the config of the official GNOME live image and then add my things 
on top of if. 
https://salsa.debian.org/live-team/live-images/-/blob/3682a17eed5223012780d1795ea0ab7d93237204/images/gnome-desktop 
looks to my like the right starting place.

Running lb config and lb build with that config, fails to find the 
package gstreamer1.0-vaapi.

I then whent ahead and reduced to config to a bare minimum.

lb config --clean --ignore-system-defaults --mode debian 
--debian-installer live --source false

With the config being just one single file 
config/package-lists/desktop.list.chroot containing the line 
task-gnome-desktop.

This time it fails configuring the package dictionaries-common.

Processing triggers for dictionaries-common (1.30.11) ...
aspell-autobuildhash: processing: en [en-common].
Error: /dev/null:1: The key "/usr/bin/aspell" is unknown.
Undefined subroutine &main::subst called at 
/usr/sbin/aspell-autobuildhash line 54.
dpkg: error processing package dictionaries-common (--configure):
  installed dictionaries-common package post-installation script 
subprocess returned error exit status 2

Can anybody point me out on how I can build and then customize a Debian 
GNOME live image?

Kind regards
Corvus