Can help You with creation of fully automated ISO install image, based on Ubuntu 18.04, which use initial settings from PreSeed config file (for initial config of network parameters/user/passwords/installing listed packages from repo, located on ISO/remove additional user creation/run post install script).
All steps/operations can be fully documented, as also embedded with info for future update of this ISO (with new/additional packages into disk repo, archive with your specific webapp/postinstall script for unpack/prepare it for run right out of the box after install).
Skill in related area present (Unix/Linux SysAdmin with 10+ years expertise), so all works/documentation can be done within short time frame.
Tnx and Regards.