Reports on report painter is created based on library which contains respective tables. Here is step by step guide:
1.Work with business and finalize GL Account grouping for each of the line items of individual report.
Finalize tables which contains all the relevant data for -Cash Flow -Balance Sheet -Income Statement -Statement of Change in equity. It could be standard GL tables or SPL or New GL table for respective ledger.
2, Find if any library already created in SAP. Otherwise create a library.
3. Create Report/ Report Group.
Please let me know if you have further question.
Thanks,
Pradip Shrivastava