Dear @tbillah
When you run your Slicer executable you can pass a python code to load the data during start time. something like the following
Slicer.exe --python-code "slicer.util.loadVolume('/full/path/to/img1.nii.gz')
or
Slicer.exe /full/path/to/img1.nii.gz
Also, you can do something similar from within the Slicer application using the python terminal
You might want to refer the Script repository for more information
https://slicer.readthedocs.io/en/latest/developer_guide/script_repository.html
HTH
Andinet