FI-SL documents have a unique source document as do most of the other accounting documents. These documents are linked with other documents via this source document. An FI-SL document is not itself usually the source document of the corresponding business transaction.
So that the DRB is able to find the link from the archived FI-SL document to the source document, you require an archive information structure for field catalog SAP_FI_SL_002. You can use archive information structure SAP_FI_SL_002 for this.
So that the DRB is able to find the link from the source document to the archived FI-SL document, the information structure should also contain field REFDOCNR.
To obtain the best runtime, you are recommended to create a secondary index for this archive information structure as set out in SAP Note 164704. Include the fields MANDT and REFDOCNR in the index. Archive information structure SAP_FI_SL_002 already contains field REFDOCNR and the appropriate secondary index.
For determining links in both directions (from and to the source document) it is immaterial whether or not the source document has already been archived.