Just use "regsrv42" ( https://www.codeproject.com/Articles/28682/regsvr-Generate-SxS-Manifest-Files-from-Native-D )
and it will create your sxs manifest with no hassle:

"Tool Usage" ( from the author's article) :

regsvr42 -client:client.exe com.dll
which will generate besides com.sxs.manifest another manifest file named client.exe.manifest. If client.exe already has a manifest file embedded, the contents of that manifest file are preserved into client.exe.manifest alongside with the reference to com.sxs assembly.

If you have more than one COM DLLs you want to use can use the tool in batch mode like:

regsvr42 -client:client.exe -batch:file_containing_com_dll_file_names
You can put all the COM DLLs inside one directory and there will be just one manifest file inside the directory named directory_name.manifest

regsvr42 -client:client.exe -dir:directory_with_com_dlls
If you have more than one directories with COM DLLs you can use the -batch function with all the names of the directories written in the batch file.

regsvr42 -client:client.exe -batch:file_containing_directory_names