Merge existing excel files into one excel file Laravel

The problem is very simple but I can't find a solution anywhere.

I need to combine a few excel files in the storage directory into 1 excel file where every excel file is now a sheet in the new excel file.

I have been experimenting with Maatwebsite/Laravel-Excel (version 3.1) but without success...
Someone an idea how to tackle this problem?

via Chebli Mohamed